Angora Haiku Generator
Angora used to be a fairly popular IRC chatroom. In addition to it's many frequents, we also had a bot, named lethargic. Lethargic was written in perl and worked by randomly selecting lines from my ~1MB chatlog file and spitting them back (after a few transformations of course)
Using a perl module that counts syllables, I split this chatlog into two files, one that contains only lines with 5 syllables, and one that contains only lines with 7. These files aren't that big, so I wrote a page that loads them with AJAX and lets you make haikus with them.