[aspen0]

There are such hacks, but they aren't needed to make your forum search engine friendly. So long as sessionids aren't used for spiders (which is true for VB3) you posts and threads will be crawled fine. If you do one of the URL rewriting hacks to put more keywords in the URL you're going to be forcing yourself to keep that URL structure forever, through all future updates (which might be hard or impossible) or you'll run into URL integrity issues, loss of backlinks, etc.

The only other things you should do are to turn the archive off (the archive creates duplicate content and typically it is less conducive to getting new registrations). Also using robots.txt block extra pages (such as backend/member/posting pages) from search engines. All search engines really need to see are the showthread, showpost, and showforum pages.

See: http://www.sitepoint.com/forums/showthread.php?t=259001