Google Groups recently relaunched with a new look and feel. One of the most popular groups in the search engine optimization community is the Webmaster Help group. This area features literally hundreds of questions about Google's crawling methodologies, as well as Web site design and its relationship to the ability to be indexed in Google. Although not all questions are useful, and responses in any community should be taken with a grain of salt, the best thing that this group has going for it is the actual participation by Google engineers and members of Matt Cutts' team.
Just in the past few days, the topics of 301 redirects and server downtime have led bloggers to cite discussion going on at Google Groups. Barry and others commented on the 301 redirect comment by Adam Lasnik, which has actually led to more questions. Both Barry and then Loren Baker commented on Vanessa Fox's statement in a response that being "down" for a few Google crawls can lead to de-indexing.
So if you have some time to spend asking SEO and other site design questions and looking for answers, Google Groups might be one of the best "forums" out there, due to the increased chances of an actual Google person being involved. If that floats your boat.