To get a site up in Google quickly, you can effectively post links everywhere that look like this:
[ url = www. compositescentral .net] composites [ /url ] (without the spaces, of course).
Spamming this all over will quickly bring Compositescentral.net on the first place of Google.
The spam that many forums receive is created by automated scripts, that automatically search forums of a particular make (VBulletin in this case), register an account, and put the above link in a useless post, or in a signature. Google drops by every now and then, crawling for links, and signals that link (either in the forum, or in a user profile). This will bring that particular site up.
Best thing is to stop robots at the door. Is there a VBulletin mod that can use the peoplesign system? I use it on my phpbb board, and in some 10 days not a single spam registration. Works much better than normal captchas.