This is a little thread for instructional art sites, online galleries, and other such "art" hangouts. Just something for reference. Feel free to add as many relevant links as you want.
deviantART - The premiere online art gallery. Very crowded, but a great place to showcase your art. If you haven't already, you should check it out.
VOID - This site has a great concept; it's a gathering of sequential (comic book) artists who create characters and enter them in "battles" with the characters of other artists. Both artists are given a time limit (usually three weeks) to complete their project (usually a three page minimum). Once the time limit has expired, other users vote on the comics, and the winner gains points (which can actually be used to buy real prizes), glory, and the right to say that what happened and their comic is what "really" happened (in other words, their character won the fight).
Check VOID out, but be forewarned, competition is tough, and honest, scathing critiques are much more common than on deviantART.
Again, feel free to add your own links.