People use ORM like Entity Framework and NHibernate a lot and I am one of them. When I use ORM, often I ma haunted by two inner thoughts. One is "This can be done in sql so easily" and the other is "What would it be like to use object database or document database? It might be fantastic." So I tried mongodb.
Installing mongodb was unexpectedly easy. You just download it and double click it. You can install it as windows service very easily like below. (from http://www.mongodb.org/display/DOCS/Windows+Service)
mongod --bind_ip 127.0.0.1 --logpath d:\mongo\logs --logappend --dbpath d:\mongo\data --directoryperdb --install
I user NoRM, which is mongodb driver for .NET. There are three C# drivers for .NET.