The maintainers of the free software you use: You're going to be building on other people's code, so give the maintainers a hand. Just as a person can never have too many comic books or hand tools, software can never have too many tests. Write some tests for your favorite tool, framework, or library, and send them in as patches. Besides letting the maintainers know who you are, you'll also make your life easier when you start your own coding. Your tests will give the maintainers an early warning when they break something you depend on.