I'm very proud (even though I could have used an existing solution) of my discussion board / weblog software, which other people and myself use daily at The Public Mooseboard and my personal blog Windlicht. I guess the pride stems from the amount of work I've put into it as well as the great feeling I get when someone else uses and enjoys what I've done regularly.

This type of pride isn't limited to programming either; I've been quite proud of some of the more complex, but still degradeable, CSS designs I've created in the past.