I've never worked hands on with something like that, but I have heard from many people Dolphin is shit.
I've heard some buzz about Ning -
http://www.ning.com/
Its Social Networking software, I haven't even actually dug into it but just on the surface I'm suspicious about how much control you have over the user data.
There's also Ska Date -
http://www.skadate.com/ been seeing ads for that around lately.
Hope that helps