Koders is a very cool source code search engine. It indexes many open source projects and covers a wide range of programming languages, including of course Java and Ruby, but also more obscure languages. Clicking on a search result brings up a very nice syntax highlighted version of the source code. Many elements in the source code (such as other class names within Java code) are themselves clickable and bring up the search results for the selected element.
This seems like a very powerful tool that could come in handy for at least two different purposes:
I’ll try to remember Koders the next time I run into one of these cases.