I have been taking a look around and the most popular .NET drivers for mongo DB all mention their LINQ capabilities.
However, I have a legacy application written for .NET 2 that I need to integrate with a mongoDB instance.
I know this sounds like retrofitting a gas turbine onto a Dutch man-of-war, but sadly migrating the legacy application to .NET 3.0 or above is out of the question.
Actually, you don't need to migrate your entire project. Since .NET 3.0 is essentially just a bunch of additional libraries (and a new compiler) for the same old .NET 2.0 runtime you could create a .NET 3.0 (or 3.5) assembly and use it safely from your .NET 2.0 code on the same runtime you're already using. You may need to include some additional assemblies however, but that's about it.
As for getting a backported driver, I wouldn't really count on it. Unless someone really needs it and can't use the suggestion I made above, and has the free time to do the work themselves it probably won't ever make someones priority list.