http://www.evolt.org - well crafted article site, if a little slow in supplying content. Most of it's well thought out and full of useful content though, with articles on technical issues and web design ideologies.
http://www.accessify.com & http://www.accessifyforum.com - one of the leading accessibility resources, with some very useful topics in the forum.
http://validator.w3.org/ (plus the rest of them sitting down the right bar) - invaluable for ensuring your code is standards compliant.
Useful Links (General Design)
Moderator: Thought Police
Useful Links (General Design)
Kajun is awaiting approval.