By "code snippet execution", I mean the ability to write a few lines of code, run and test it without having to fire up an IDE and create a dummy project.

It's incredibly useful for helping people with a small code sample without creating a project, compiling everything cleanly, sending them the code snippet and deleting the project.

I'm not asking about the best code snippets or a snippet editor or where to store snippets!

For C#, I use Snippet Compiler.

For Java, I use Eclipse Scrapbook.

For LINQ, I use LINQPad.

Any suggestions for other (better?) tools? e.g. is there one for Java that doesn't involve firing up Eclipse?

What about C?