There is currently a very promising project called
Drupaltin, to integrate Drupal and vBulletin in a fully modular way (e.g. no hacks to the core of either Drupal or vBulletin). It's currently an alpha release, but already working terrifically in my tests. I've been following it closely myself and trying to help as much as I can. It's for Drupal 5 (probably not 4.7), supports seamless bi-directional account management, and has a great
feature roadmap.
If any of you have tried out Drupal in the past and didn't like it, I suggest you give it another look now - version 5 is exponentially better than all of the previous versions. If you need a good kick-start on learning a bit about Drupal,
here's a thread I wrote the other day that lists a number of helpful resources (including articles, lessons, screencasts, etc). I also wrote a thread
comparing the current 3 Drupal+vBulletin integration options. Drupal's recently been used to make a number of high profile sites such as MTV.co.uk so it's really stabilizing as a great platform for community-centric and social networking sites.
Anyhow, I will be building a pretty large site around this solution (converting my current forum of 18,000 members), have spent months researching and planning it, and it looks like it's going to be "the one" I've been searching for. If anyone would like to head over to the Drupaltin site and offer their feedback and help then that would be excellent (I'm not the developer by the way - just a member interested in seeing the project completed). If you can, check out the plans for
upcoming features, and if you have knowledge in those areas, lend a hand