What are some good forums / groups / directories that can be used to promote a web site? The best ones would be visited by a lot of people, ranked nicely in Google, and easy to post and put a link in.

To start, so far I've used Yahoo! Answers and Google Groups. Both get indexed fast and are pretty busy.

I tried MSN groups but they are a real mess, with more spam than real posts, hard to find specific subjects and not really worthwhile.

Any others?