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. It is sort of like a tutorial.
Part I - Reusable IQueryable base classes Part II - Where and reusable Expression tree visitor Part II - Local variable references Part IV - Select Part V - Improved Column binding Part VI - Nested queries Part VII - Join and SelectMany Part VIII - OrderBy Part IX - Removing redundant subqueries Part X – GroupBy and Aggregates Part XI - More of everythingPart XII - Relationships and the IQ ToolkitPart XIII - Updates and Batch ProcessingPart XIV - Mapping and ProvidersPart XV - Transactions, Sessions and FactoriesPart XVI - Performance and CachingPart XVII - Automatic Caching and Loading Policies
The source code found in this series is also available at CodePlex.http://www.codeplex.com/IQToolkit