I'm using customized php code for most of my website, and are using different vbulletin hacks to show online users/guests, login-box, latests posts, forum stats etc. These hacks are all available at vbulletin.org, you just need to do some searching.
A great option I recommend is using Coranto + vBcomments for news and comments, that's sweet.
I've heard vBhome Lite is nice, it's using very little resources. You don't need to use all options that are included in vBhome, many are selectable, so I think it could be a nice alternative for your site.