CodeZoo
CodeZoo exists to help you find high-quality, freely available, reusable components, getting you past the repetitive parts of coding, and onto the rest and the best of your projects.
Additional to just offer the download CodeZoo also offers forms to let users exchange tips and reviews about a given component. There are also always links to related O'Reilly books on the component pages ;-)
The site currently only offers Java code but using the "Feedback" form you're asked to suggest additional languages. I'd really love to see some C, C++ or Python components ;-)