Yale C/AIM Web Style Guide - Perhaps the
most cited site (get it?) for web design. Though full of good advice,
it is not universally praised. See the Critique of Yale Style Manual for an alternative
view. Personally, I like it's feel alot.
Useable Web - 1133 links about Web Useability. Well organized by topic.
Writing for the
Web - Jakob Neilsen's view of how content should be laid out on
the web. He's a strong proponent of simple, clear websites, as you will
see.