I've spent some time off and on over the past few weeks implementing what's essentially a structured write cache with MongoDB for W3Counter.com. It handles large volumes of writes, and counters (the equivalent of SQL UPDATE table SET col = col + number) very, very well. This is something a lot of the other NoSQL data stores, like SimpleDB, don't handle very well. I might just have to go to this conference.

MongoDB is one of the few open source projects that I'm really excited about. I'm seriously considering flying over to SF (I'm a broke college kid in Boston) just to be a part of it.