LINQPad is a handy tool for anyone who works with LINQ:
LINQPad is more than just a LINQ query tool: it's a code snippet IDE. Instantly execute any C# 3 or VB 9 expression or statement block!
Best of all, LINQPad is free and needs no installation: just download and run. The executable is under 2MB and is self-updating.
Fun!