Are there any platforms / sites where people can share expertise in game development and where you can share (either payed or free) digital content (like images, sounds, animations but also frameworks or libraries) to be used in games? I'd also like the possibility to contact users and request specific pieces of content.

I'd like to start out as an indie developer and have programming skills but I lack the experience and time to create ingame artwork and sound. Is there any site where I could locate other people (artists mostly) who would want to work on a game for free?

I know I can get most technical questions answered on this site and I have some contacts but I'm affraid this won't be enough.