Are there composer/artist communities like gamedev is for (mainly) programmers and deviantArt for artists?

You can try http://www.dmusic.com, which both allows users to upload their music and entertains a forum. In actual fact, it's said to have previously been the partner site of Deviant-Art.com

I would recommend www.acidplanet.com. I was a member there for years and really learned alot for reviewing other people's music, having my own music reviewed and doing collaborations with other artists on that site.

I don't know if you have to be a registered user or not- its been three years since I became a member. Check it out. My profile is: "nsmads". I have alot of serious and silly songs on there. I don't post music much on there any more since most of what I write is under copyright of my clients.

Hope that helps,

Nate

www.soundclick.com

Decent set of forums, with enough knowledgeable people to make your time spent worthwhile. There's a critics review board if you want to get some of your stuff reviewed; I actually run a thread of my own on the board. Plus, they offer unlimited hosting for your songs if that's an issue for you. Check it out.