While on my quest to learn everything I can about photoshop, I came across
these two links that I thought might interest some of you.
http://www.gfxartist.com/
I've only scratched the surface of this one, but has galleries and tutorials
by some well known artists buried in there.
http://www.conceptart.org
(for me) the best part of this one is the 'Daily Sketch Group' area of the
forums. The moderator puts up a new topic every day and you are supposed to
spend no more than 90 minutes on it and then show your results, both digital
and standard media are acceptable as long as you have some way to upload the
results to the web.
Both of these are 'user beware' as they have 'open forums' and even though
they have moderators, moderators don't catch everything. But for advanced
students these might be worth pointing them in the right direction.