Of all quoted above, I particularly like http://www.webdesignerforum.co.uk. You can check out some of these forums already listed and pick up the one you find adequate to your demands.
Yeah I have to agree with you, webdesignerforum.co.uk is pretty sweet! I have joined, it seems a little new, but the people are great! Plus there's no "In Your Face" advertisements like you see on alot of forums nowadays.
This seems like a nice way for forum owners to promote their stuff if theirs is related to web design Anyway, DP is a good place for designers, too. Isn't it..
i found one place where you can display your art design work... www.webdigity.com...if i'm not mistaken...haven't joined yet but you can check it out.