I've been into the 2600 homebrew scene since "Making Games for the Atari 2600" came out a few years ago. I haven't made anything useful yet, but the community is great and very active. There's an awesome twitch channel[1] dedicated to 2600 homebrew, ZeroPageHomebrew. They do 2 shows a week, ~2 hours each. The developers and various AtariAge people are usually active in the chat. They're doing an awards show in February for homebrews made last year.

[1] https://www.twitch.tv/zeropagehomebrew