DotNetNuke
I've been running Rainbow for a while now at http://www.stevex.org/dnn, and I just installed the DotNetNuke portal toolkit. It's quite a change, and I think it's a change for the better. I'm going to write up some of my experiences with both, but in the mean time have a look at the new site.. there's not much there yet I'll be populating it over the next few days.