Java libraries, CPAN, and the Unix/C universe of libraries are three examples. But you should only check them out if there's a library that does the specific thing you want.

Yeah, I really have to second this one. It's not just the UNIX/C universe, though -- it's the UNIX scripting universe. As a particular example, how do you tie your graphing software to your analysis software to your screen scraping software? You could try writing them all in Python -- or you could just use pipes and tie together GNU plot and wget with some custom filters in Python. It takes a few years to get confident with this stuff; but once you are, you will never write so little code :)