TravelMob is travel site meets Evite. It lets you create a trip homepage, invite people, manage RSVPs, upload important files, create a photo gallery, see top tours for your destination, and plan via message board. There's a Facebook-style newsfeed that shows what everyone on your trip's doing.
I'll be attending SaaS Summit 2008 this week in San Fran. Lots of interesting speakers talking about trends in Software as a Service and Web 2.0. Let me know (contact info) if you'll be attending the conference or are in the area and would like to get together.