Anyone who is familiar with LINQ To SQL knows about Matt Warren's series of blog posts to help one develop an IQueryable Provider. Check out Matt's posts here.
In addition to his series of posts, Matt has provided source code that serves as a library of common code that you can use to develop LINQ IQueryable Support in your O/R Mapper.
The project is called LINQ IQueryable Tookit and described as follows:
"IQToolkit is essential if you are building your own LINQ IQueryable provider. It contains common tools and source code you can apply to your own project.
In the toolkit you will find useful techniques for manipulating LINQ expression trees, implementing IQueryable providers, and a host of extensible components for building providers that target translation of LINQ expressions into SQL like languages."
You can download the LINQ IQueryable Toolkit here.
If you are annoyed that LINQ To SQL is dead and have little faith in the Entity Framework, check out a list of O/R Mappers to use in your .NET applications.