One of the things that may not be apparent if you are new to Language Integrated Query (LINQ) is that you can go beyond the "in box" LINQ to Objects, LINQ to XML, and LINQ to ADO.NET (DataSets/SQL/Entities).  OakLeaf Systems is maintaining a running list of some of the community projects currently going on to LINQ enable Amazon, MySQL, NHibernate, SharePoint, Flickr and many more.  Details here.

-Marc