I'd like to go ahead and sing my praises for a free script I found about a month back - it's called "
Rusnak PHP Adoptables," and it's basically a complete (albeit somewhat simplified) package for an "adoptables" website.
Ever come across a forum where half the members seem to have a little pixel pet (or several) in their signature? That's an adoptable. When the user gets enough other people to click on it (thus redirecting them to your website), the pet "grows" into another form.
The beauty of a website like this is that all the users generate constant traffic for it. I had been looking for a script that could do something like this for a long time, and even considered hiring someone to code it.
I don't know if anyone else has thought about creating a website like this, but if you have, here's a decent free script for it. I'm not a

e fan of the default template or the organization, but I'll work with it long before I'll pay someone $300+ to code something better from scratch.
Just thought I'd post this here, since this isn't a particularly well-known or common script and I had to look around for quite some time to find it. Hope this helps someone!