If you are using LINQ-to-SQL, it is often helpful to see the SQL generated and the resultant query results.  You can do this, even while debugging, with the LINQ to SQL Debug Visualizer.  Debug Visualizers are the dialogs that pop up when you hover over a statement and click the little magnifying glass in the hovering menu.

I believe by default Visual Studio will show you the generated SQL when you over over a LINQ statement, but there is no way Debug Visualizer to help see the SQL in a more user-friendly view.  Scott Guthrie gave a blog post describing a simple download that can give you this enhanced view of the SQL, and even the ability to execute the query and see the raw data returned from your database:

http://weblogs.asp.net/scottgu/archive/2007/07/31/linq-to-sql-debug-visualizer.aspx

Included in the post are instructions of how to extract the necessary DLL library, and where to place it in Visual Studio’s file hierarchy.

A really simple enhancement for working with and debugging LINQ-to-SQL that is definitely worth the minimal effort to acquire it.