best intergration combination

I have been looking around for quite a while at several pieces of software I would like to use (and some which I already do use). I am hoping to be able to integrate them all so I don't have to get everyone to sign up separately for everything.

Currently I use G2 and phpBB2. I want to stick with these and continually upgrade them whenever patches come out.

Does anyone have any suggestions on a cms that integrates well with these two?

Thank you