I just learned about a search engine called Krugle (http://www.krugle.org). It lets you search billions of lines of code in open source projects around the world.
It's really a pretty neat thing that they've done. There are many times that we need to write some complex sort of code that someone else must have had to write too. Why not see if you can re-use it and save yourself the time.
The engine is aware of source code structures, so you can select your language and then search for the keyword in certain locations like class names, function names, function calls, etc.
They've got content for MS technologies too: ASP.NET, C#, VB.NET, SQL, etc.
Pretty neat stuff!