I wonder if there is something like a standalone Version of Visual Studios \"Immediate Window\"? Sometimes I just want to test some simple stuff, like \"DateTime.Parse(\"bla
Well, this isn't a direct answer to your question, but you could look at this tool:
Also, if you want to see the IL produced, or similar, there is a tool that plugs into Reflector, called Snippy, based on the Snippy tool that Jon mentions in his own answer further down.
All of these are very nice to use.