LinqToRdf is a Semantic Web framework providing a full-featured LINQ query provider for .NET allowing you to use SPARQL to query remote semantic web databases. It also provides graphical design tools for Visual Studio .NET 2008 with a UML style design surface for the production of both turtle files and .NET domain models.
For more information go to the project wiki. Alternatively you can check out Andrew Matthews' blog for historical information. Send email to linqtordf-discuss@googlegroups.com to ask questions or go to the project site to request features.