[NateLipscomb]

One good source is Behance (behance.net). A lot of good game artists have profiles and portfolios on there. You can message them directly or post a job for applicants.

Odesk (odesk.com) also has game artists, although the quality is all over the map. You can post a job description and review the portfolios of the artists that respond to find a good fit. They allow you to do a short "working interview" project, too, where you have the artist spend an hour or two creating a piece or two of your game art so you can see how well they will execute your vision, how they are to work with, how fast they can produce, etc.

I haven't used twitter to find game artists before, but I'd image if you look for the right hash tags, you could send out a request for available game artists and get some responses from available folks.

Good luck.

[ronyeh]

Behance looks good. Thanks for the tip!

I'd rather avoid generic contracting/freelance sites, as I feel like the quality would be "all over the map" as you say.

I'd prefer looking for artist communities, especially if they have forums that talk about iOS/Android game art.

[NateLipscomb]

No problem. Although I think Behance is probably better for your purposes, you might also want to check out DeviantArt (deviantart.com). It's another pretty big artist community, although I'm not sure how many game artists are on it.