Embedding RavenDB into an ASP.NET MVC 3 Application
I am particularly fond of RavenDb. It's definitely worth a look, as is this tutorial if you aren't sure where to start with it. There is some fair (not great but ok) documentation on the RavenDb website as well last time I checked.
I have just recently downloaded a later version and small things that immediately pleased me was a bit of an upgrade to the RavenDb documents interface itself. It's definitely maturing.