Stick It In The Slot: Absolutely hilarious piece of parody.
PC Atari Emulator: John Dullea's PCAE emulator. Warning: Frames!
Stella: The Stella emulator for the Atari 2600. Warning: Frames!
Giant List of 2600 Label Variations: John Earney's list of label variations.
Bob Colbert's 2600 info and SC files: Lots of developer tools for the Atari 2600 and Supercharger.