mkportal.it is a good powerful CMS for both vB and IPB and a couple of others. It can convert the forum skin over to it's self well if you find a good one. That's twice I've mentioned this here today, feel as though I'm plugging the damn thing, lol
For CMS, I'd go with Drupal. There is a mod at vbulletin.org which will integrate your forum theme and database into Drupal very easily. It's not incredible as far as looks and design are concerned, but it gets the job done. You can see an example of it at my site - http://www.adminfusion.com
Just a heads up, there are very few good free skins. I'd advice purchasing one or developing your own.
vbadvanced is the perfect CMS While I don’t advise you to use free skins, I searched all over the internet and very very few skins are worth it! While with 30$ you can buy a very professional skin!
For CMS options, really the only decent options that are free have already been mentioned: vBadvanced CMPS and vBDrupal. For skins, best-board.com, vbulletin.org, and vbulletin.com would be good places to start, but if you want something nicer, you might want to buy a cheap skin from something like vbskinworks.com.
I'm using vbadvanced and I love it. I recommend it to anyone whos looking for a CMS/portal for their vbulletin.
I love mkportal (ww.mkportal.it) Full features and support! Go to www.mkportal.it for more informations!