Brightkite: Location-based social network. Each location has a "placestream" that records all the activity that ever occurred in that location. I like the real-time view of one's friends.
Artist Exploder: For musicians, turns Facebook into MySpace. Artists can build a FB app in 5 minutes. I get the need for musicians to be able to get on Facebook. I worry about whether the business is sustainable. Sounds like they're off to a good start though.
Occipital: Sci-fi artificial intelligence for photostreams. This is some very cool technology. 1) They use the GPS tags and timestamps on your photos to locate them and group them. 2) They scan your photos and compare them against a landmark database to figure out what's in your photos. 3) They can automatically detect common objects within your photostream. 4) They can even generate 3D walkthroughs based on geometric analysis of your photos.
I have no idea what this technology will be used for, but it is way cool, and the founders are technical rockstars.
App-X: SFDC for private equity and VC. App-X is an SFDC application for fundraising, dealmaking, and portfolio management, including iPhone support. Totally makes sense. Don't understand why they're raising money--I'd bootstrap it. I think they're here to pitch for customers!
Interesting fact: SFDC seats are free for non-profits.
EventVue: Conference-based social network. Attendees tag themselves, say what they're looking for, add in things like blog/LinkedIn/Twitter, and can message each other. The value to conference organizers is simple: When people know who's coming, they'll be more likely to register. You can see which of your LinkedIn contacts are attending, for example. EventVue focuses on conferences, not trade shows--high attendee cost and quality. Wendy Lea, Eric Norlin, and Dave McClure are all on board (nice company!).
I like it, and I can see why conference organizers would adopt the product.