I'm an unabashed fan of MongoDB, the only NoSQL database just about everyone has heard of. Clients of my consultancy like MongoDB a lot because it performs well and scales out using commodity servers. Developers love it because it supports a flexible data model that makes building apps much easier than with SQL databases.
It's no shock, then, that I flew up to New York last week for the first-ever MongoDB World event. I walked away impressed at how MongoDB has grown up.