 <p>The mongodb-csharp driver is about to make a huge push regarding support for typedcollections which will include full Linq support. I think you'll find that it is easy to work.</p> <p>The other 2 projects are also steaming ahead. If you want .NET 4.0 support, simple-mongodb would be your best bet.</p> <p>NoRM has a whole bunch of committers who are all great coders, so no problem with it except it doesn't have an official release.</p>