LinqPad looks great!
This tool lets you develop LINQ queries by playing with them against live data!
I find that the ability to quickly dev/test queries live is hugely productive, and that’s one reason I like working with data. Now all you Linqies can enjoy that too!
The installer is low to zero footprint, but relies on you already having .Net framework 3.5 or 4.0.
The basic version is free, but not open source.
There is a paid upgrade to get intelli-sense and code snippets.
Here is a shot of what you can do with our familiar QA project.