Where to get this web application?

I’ve got an idea for a website, but do not where to get the application for it. Basically, I’m looking for something similiar to UrbanDictionary.com. It will be the same basic idea, but the content would be different. It could be ASP, or PHP. I’m familiar with MySQL, and could learn others. Is there any free code out there that can do this? I can buy it too, if it’s what I’m looking for.

You could try looking here at the CGI Resource Index for something that would fit what you are looking for.