We have been hearing a lot about NoSQL databases over the last couple of years. If you are curious about what the good and bad things about them who better to ask than the nice folks over at Database Journal. They wrote a great article that should help you get started on your path to determinng whether NoSQL databases are right for your next project. There were several other links on the page pointing to deeper discussions on the topic of NoSQL databases. It's a very balanced and well thought out article worth the time to read.