Many people have helped in some capacity with Stella development over the years. Some provided technical help while others have offered suggestions and praise, or donated hardware to help the project. The Stella Team is grateful for all the help and support it has received over the years. The following is a (likely incomplete) list of the people who have played a part in bringing Stella to you:

Main Developers  
Bradford W. Mott (retired)
Original author and creator of Stella. The inspiration for the entire project, it goes without saying that without Brad, there would be no Stella project at all.
Stephen Anthony
Ported Stella 1.1 to SDL. Added extra command line options to X11/SDL versions. Added INI file support, faster startup, snapshot support, and pause functionality to core. Converted Stella 1.1 manual to HTML. Ported codebase to SDL for Windows/MacOSX. Added OpenGL support and Stelladaptor/2600-daptor support. Current maintainer for the Linux, MacOSX and Windows versions. Currently the main developer testing Linux builds.
Eckhard Stolberg
Provided a description of the TIA bug that produces the star field effect in Cosmic Ark, provided the PAL television palette, and participated in a helpful discussion on understanding the TIA's RESPx multi-sprite trick. Provided the Commavid, Megaboy, 4A50 and X07 support for Stella as well as some improved Supercharger BIOS code.
Thomas Jentzsch Emulation core development, jack-of-all-trades. Helps with issues all across the codebase, including emulation fixes, UI themes and all things UI-related, etc. Currently the main developer testing Windows builds.
Christian Speckner
Provided a completely new TIA core in Stella 5.0 and TIA sound core in 6.0 (based on work by Chris Brenner), and helped perfect nearly all other aspects of emulation. Currently the main developer testing Mac OSX builds.
Brian Watson (retired) Helped with getting the illegal CPU instruction support working with Stella. Brian also submitted a number of other changes, such as debugger support, which have been finally integrated into the 2.0 release of Stella. Without a doubt, there would be no debugger support in Stella if not for the tireless work of Brian.
Special Thanks  
Stephen Ahrens (aka 'Amstari') Generously donated a PAL CompuMate to help with cassette load/save functionality.
Ian Bogost and the Georgia Tech Atari Team
(CRT Simulation Project)
Contributed code for the 'CRT simulation' OpenGL filters. The Winter 2009 team members are Edward Booth, Michael Cook, Justin Dobbs, William Rowland and Prince Yang.
Also contributed Blargg filtering code, a version of which was integrated into Stella 3.7.
Chris Brenner (aka 'crispy') Generously donated C code from his FPGA project that accurately models the TIA sound circuitry, which has been adapted for use in Stella 6.0 by Christian Speckner.
Andrew Davie and Thomas Jentzsch
(Boulder Dash)
Generously donated a Boulder Dash cartridge, and specifically mentioned Stella in its manual.
Robin Edwards Generously donated a UnoCart flash cartridge.
Tom Hafner
Generously donated a 2600-daptor, 2600-daptor II and BoosterGrip controllers, as well as sample code to help with development. Also donated a very generous monetary contribution.
Richard Hutchinson Generously donated an AtariVox USB adaptor to help with AVox development.
Thomas Jentzsch Provided updated NTSC palette, many bug reports and debugger feedback.
Also generously donated a Star Castle Arcade cartridge.
Andrew Kator
Provided PHP and CSS code for a major update to the Stella website, as well as a monetary contribution.
Richard Kennehan Generously donated Atari light-sixer, various controllers, and several games to help in testing ROMs on a real system.
Alexandre Liduario Generously donated Atari PAL-M console to help in testing ROMs on a real system.
minimoose Donated a very generous monetary contribution. Thanks for the support!
Tifany Oslin Generously donated a 7800 console with video mod and several games, and also several monetary contributions. Thanks for the support!
Fred X. Quimby (aka 'batari')
(Batari Basic)
Generously donated several Melody and Harmony Cartridges to help with development, and also donated a collectors edition of the Harmony Cart (release version including the cart, CD, SD card, etc).
James Randall (aka 'toymailman') Generously donated a 7800 console and several games and manuals to help with development.
Darrell Spice Jr.
Author of the OS/2 version of Stella.
Also generously donated Medieval Mayhem, Space Rocks, Stay Frosty 2 and Stella's Stocking cartridges.
D. Scott Williamson
(Star Castle 2600)
Generously donated a copy of Star Castle 2600 CIB, and (as promised on the Kickstarter webpage) a very generous portion of the CD proceeds. Also specifically mentioned Stella in its manual. Thanks for all the support!
Albert Yarusso
Provided helpful feedback for the MacOSX port, and generously donated hardware and monetary contributions over the years.
Anonymous Donated different items over the years, but wish to remain anonymous and/or didn't get back to me with contact info (thanks for your support, even though nobody will know who you are :))
8-Bit Classics
Offered a very good price on a Commodore 128D
Eugenio "TrekMD" Angueira
Donated several 7800 games in appreciation of the project
Provided much feedback and testing which eventually led to a fix for the infamous ATI OpenGL 'red screen' issue
ArgentStar Donated a monetary contribution
David Aspell Ported release 0.7 of Stella to Java
Christopher Bennett Helped discover a Superchanger emulation bug in release 1.0 of Stella
Alexander Bilstein Provided "A Brief History of the Atari 2600" for this manual
Black Umbrella Design Donated a monetary contribution
Dan Boris Provided technical information on the Supercharger
Robert Buchanan Donated a monetary contribution
"Uncle" Carmine
Donated several 2600 games and manuals to help with development
Piero Cavina Allowed "Oystron" to be included in the Stella distribution
John W. Champeau, Champ Games Donated a monetary contribution
Bob Colbert Allowed "Okie Dokie" to be included in the Stella distribution
Joe D'Andrea Author of the IRIX port of Stella until release 1.2
Daniel Delorme Donated a monetary contribution
T. Drobot Donated a monetary contribution
Joe Durnavich Donated a monetary contribution
Electronic Sentimentalities Donated a "7800 AV Mod Board"
Sascha Eversmann Donated several monetary contributions
Renato Ferreira Provided code to support private colormaps under Unix
Stephan Freudenreich
Donated a monetary contribution
Ron Fries Author of the awesome TIA Sound library
Óscar Toledo G
Donated a monetary contribution
Aaron Giles Author of the Power Macintosh version of Stella until release 1.1
Goldenegg (on AtariAge) Donated a monetary contribution, and provided feedback/testing for OSX versions
David Gratt Donated a generous monetary contribution
Mark Grebe
Author of the Macintosh OSX version of Stella from releases 1.4 to 2.4; helped with Stelladaptor support
Sean Green (Bliss-Box)
Donated a Bliss-Box adaptor to help with development
Darryl Guenther
(20th St Arcade)
Donated a monetary contribution
Mark Hahn Allowed "Elk Attack" to be included in the Stella distribution and provided help with the TIA HMOVE blank bug
Ulrik Hansen Donated a monetary contribution
Pitfall Harry Donated a monetary contribution
Alex Herbert Provided much information on AtariVox and SaveKey functionality
Michael Hewitt Donated a monetary contribution
Kevin Horton Author of the definitive Atari 2600 bank-switching document
Michael Jo Donated a monetary contribution
Ryan M. Johnson Donated a monetary contribution
Erik Kovach Author of the property file for release 0.7, 1.0, 1.1, and 1.2 of Stella; donated a generous contribution
Matthew Logue (Matalog) Donated a monetary contribution
Austin Mackert Donated a monetary contribution
Sandro de Oliveira Maia Donated several monetary contributions, and provided words of support
Donald Maley Donated a monetary contribution to help with CompuMate development
Daniel Marks Provided improved keyboard joystick support for Stella release 0.1
Ralf Matz Donated a monetary contribution
James Mcclain Provided patches for the 1.2 release to get Stella to compile with GCC 3.0
Cam McCormack Donated a monetary contribution
David McEwen Author of the Acorn version of Stella
Jeff Miller Author of the Windows version of Stella until release 1.2
Nick Montfort and Ian Bogost
(Racing the Beam)
Specifically mentioned Stella in their book
Dan Mowczan Provided a Supercharger to help with Stella's development
Kostas Nakos Author/maintainer of the WinCE version of Stella from releases 2.0 to 2.3.5
Matt Nicholson Donated several 2600 CIB games and Atari 800 items
Eric Nikolaisen Donated a monetary contribution
Jack Nutting Author of the OpenStep version of Stella
Omegamatrix Provided test ROMs which led to more accurate emulation for SWCHx/SWxCNT and RIOT behaviour, and for 'illegal' TIA reads
Owen (loltpily21) Donated a monetary contribution
Chris Papademetrious Donated a monetary contribution
John Payson Provided EEPROM emulation code for AtariVox and SaveKey support
Wilbert Pol Provided many ideas and some sample algorithms for greatly improving 'illegal HMOVE' emulation
Manuel Polik Author of the Windows version of Stella (Cyberstella) starting with the 1.2 release until its retirement
Jim Pragit Author of the "Game Menu" emulator game shell
David Racette-Campbell Donated a monetary contribution
Brent Robbins (aka 'Schizophretard') Donated a very generous monetary contribution :)
[APG] RoboCop Donated a monetary contribution
Jasen Rogers Donated a monetary contribution
(RomHunter ROMs)
Provides an updated database of ROM information on a regular basis
John Saeger Participated in a helpful discussion on understanding the TIA's RESPx multi-sprite trick
Chris Salomon Provided information and code to help implement Supercharger support
Filippo Santellocco
Donated a monetary contribution, and mentioned Stella in his homebrew game manual
Glenn Saunders Donated a Supercharger to help with Stella's development
Jason Scott Organizer of the property file archive for early versions of Stella
Seagtgruff Provided test ROMs which finally fixed all remaining issues with ADC/SBC opcode decimal mode emulation
David Shaw Provided make targets for the BSDI platform
Raul Silva Helped with design and graphics for an early version of the Stella web site
James Smith Donated a monetary contribution
Chris Snell Maintained a mirror of the Stella FTP site
Spacedueler (on  AtariAge) Donated several homemade 'spinners' to help with testing the mouse "specific axis" mode
John Stiles Maintained the Macintosh version of Stella until release 1.2
Matthew Stroup Author of the Amiga version of Stella
Richard Summers Donated a monetary contribution
Joel Sutton Author of the FreeBSD version of Stella
thegoldenband and toiletunes (on AtariAge) The former for creating a cartridge auction and donating the proceeds, and the latter for winning the auction
Greg Troutman Allowed "This Planet Sucks" to be included in the Stella distribution
Robert Tuccitto Provided valuable bugtesting and feedback which finally helped in fixing a long-standing lockup which occurred after Stella has been running for 71 minutes, and donated a monetary contribution.
Ultimate Patches Donated a monetary contribution
Curt Vendel Provided schematics of the TIA which are being used to improve the TIA emulation.
David Voswinkel Maintainer of the PSP version of Stella starting with the 2.0 release until release 2.2
Keith Wilkins Maintained the DOS version of Stella until release 0.7
Sheldon Williams Donated several trakball controllers to help improve emulation in this area
Jeff Wisnia Provided technical data sheet for the 6532 RIOT chip
Gareth Woodham Donated a monetary contribution
Alex Zaballa Maintainer of the GP2X version of Stella from releases 2.1 to 2.3.5