Generating random passwords using easy to guess words.
This idea was based off the XKCD comic http://xkcd.com/936/
Bear in mind that I really don't advise using this as a way for you to create passwords for your own use, as all the words are in a common place - /usr/share/dict/words - which makes it an incredibly easy source for someone wanting to brute force your password. The idea is that your password comes from completely random words joined together, picked from seemingly nowhere. That, and the source code to this password generator is out there, so it's easy to "reverse engineer" - i.e. look at the source code - and formulate easy plans to brute force your passwords.
If you really need a good password generator, look into KeePass. It's open source to boot, but the algorithm behind the password generation is far more cryptographic (read: secure) than this source code ever will. This, for me, was just an opportunity for me to use Perl.
I strongly suggest you don't bother using it for real world use, but only for educational use.