DeviantArt - deviantART was created to entertain, inspire, and empower the artist in all of us.
Behance - The Creative Professional Platform.
BlabJam - A crowd moderated Pixel Art Editor where you create and share art and descriptive text for free in...
ArtStation - ArtStation is the leading showcase platform for games, film, media & entertainment artists.
Logamp - Share your creation such as music, art and literature. Get sharing, it's free.
pixiv - pixiv is an illustration community service where you can post and enjoy creative work. A large variety of work is uploaded, and user-organized contests are frequently held as well.