Here's a list of all the posts in the building an IQueryable provider series. If you want to get the latest and greatest source code just follow that last link. If you want to discover how to build your own IQueryable provider read from the beginning.
Bart De Smet wrote a hands-on tutorial that explains quite in-depth how one can build a custom data provider that is LINQ enabled using IQueryable. When completing Bart's "IQueryable Tales" tutorial, you'll have created a simple LDAP data provider that
Here we link to tutorials that explain how to build LINQ providers and, thus, make a data source accessible through LINQ.
As an example that will be included in the Linq in Action book, I've created an example that shows how Linq can be extended to query anything. This example introduces Linq to Amazon , which allows querying Amazon for books using Linq! It uses Linq's extensibility