Jacob1's mod is probably the best (completely a matter of opinion, though)- it keeps pace with and is probably ahead in development of the game, has a bunch of cool features, and feedback is easy.
@johnpears2(View Post) It was started back in 2008 I think (?), but I wasn't even around back then, I didn't find it until 2011.
For c++ modding, there's me, RCAProduction, FeynmanLogomaker, maybe Lord_Bowserinator, and maybe whatever BMN is doing but don't know about that. But it really isn't that active anymore.