Google has launched Google Code Search a place where the developers can access the publicly available source code.
Google Code Search is really a great resource mostly for web developers and hardcore programmers. Eventhough these application can be used for good reasons hackers/crackers may use it in a different way to find illegally posted source code and may use it in evil ways.
For those who dont want google to crawl the code can add up a file called robots.txt in their website. For more info check out here