There are a number of tools that are useful for 2600 development, with the emulator also being usful for those of you who are only interested in playing homebrew 2600 games.
- DSAM is an open source assembler that supports a number of different processors including the 6502 line of processors that the Atari 2600 uses. It is located at http://dasm-dillon.sourceforge.net/
- Stella is an open source Atari 2600 (VCS) emulator. While emulation is not illegal, copyright infringement is. While it is fine to use an emulator to create your own games or play games that have been obtained legitimately (such as the games on this site), using emulators to "pirate" games is not a legitimate use of emulators. http://stella.sourceforge.net/
- For those of you who are interested in playing with the 2600 but are overwhelmed by assembly language, there is a simple basic compiler. I have never used this so have no idea how good it is, but it is an option. http://bataribasic.com/
If you are aware of other tools that may be of interest, please feel free to contact me and let me know about them.