I was a little surprised to read about Confabb this morning. I've been working on a similar type of application, ConferenceMeetup, in my spare time.
After going to a few conferences, I really wanted a tool that could help me connect with other people while at the conference, so I built one. The idea behind the app is to provide a private community site for conferences where their attendees can learn about each other, connect with each other, and provide feedback to conference organizers and presenters about the presentations.
It's been a fun project, partly because Rails makes it so easy to build these types of applications. I think that ConferenceMeetup would be useful to have at any conference. In fact, I appreciate the validation of having some smart people agree with me on the value of having such a service. :)Update:
After reading Tim's comment for this blog post, I was reminded that I didn't mention Web Connections (which I had intended to do â€” sorry, Tim!), the app that he built that has the same sort of theme. I saw his app after building ConferenceMeetup and I really liked it. I agree with his comment that it really is about the community of people that are participating in the conference. Connecting with the people there makes the event much more enjoyable.