This Google feature is still in experimentation stage but is available for public usage. I am very much impressed they have thought of this developer-friendly search. The feature, unlike the usual web search, returns pages that includes individual files, mostly source codes of different programming languages. Upon searching again and again, I have observed that Google Code Search spider is crawling only files with codes available for public viewing, generally open source; even zipped, compressed libraries of files; and public SVN and CVS repositories.
Google Code Search
http://www.google.com/codesearch
I like this idea since it will help developers like me to search for specific classes or functions. I can even search using the author’s name or email as keyword and get the results I want.
If you are a developer or programmer, this tool is a must for you to have!

Can also use it to hunt for PHP source installer files. Vbulletin’s still fighting this…
Their source installers should have different copyright than the rest of their open files. Best thing is not to put those source installers in a publicly available URLs.