I have been thinking about transforming my vbulletin forum to some wordpress blog however it does not seem like its an easy process. I have researched around for any convertor but there is nothing turning up.
WP + BBPress. Perform a look for BBPress import from vBulletin and find out what you could find. There must be BBPress plug ins for your, but, since I am not vBulletin user, can't help much more.