Mike Dodaro has an interesting article up on the schema for mapping using the Entity Data Manager which should ship with the Orcas release.
Having been a champion of ORM tools for a while now I am really keen to see this released. There still remains a core of MS world developers who will not shift their paradigm to begin using these kind of tools until Microsoft starts shipping them.
We use the excellent Wilson ORM on my current project, which in itself derived a lot of its API from the failed attempt to deliver ORM tools in the .NET 2.0 release of the framework called ObjectSpaces. That said Wilson is probably best aproached by those of you with an understanding of how ORM tools work as documentation is really by source, example, forums, and trial and error.
IMO the biggest issue is to get people to give up their home-rolled code generation solutions in favour of off-the-shelf ORM tools for a lot of use cases. The cost of buying a tool is usually a lot cheaper than the cost of rolling your own (and the pain).
There area lot of players out there. I tend to think of them pretty much as different cuts of steak. You can roughly divide them into reflection (i.e. Wilson) and code generation (i.e. LLBGen Pro) based in approach. When evaluating you want to look for support for things like .NET 2.0 support (generics particularly but also nullable types), support for stored procedures supplementing your mapping (there is always something you want to do that is not quite out-oft-the-box so you will need some mild extension ability), and support for sessions (including identity maps et. al).
A lot of people swear by LLBGen Pro. I should also give a plug to XPO for my friends and Developer Express like Oliver Sturm.