Running http://www.clickrouter.com - worked out well because I needed it for my other projects and it was an instant revenue win for those use cases alone.

Spruced it up (could use more I know) and opened it to others thereafter. Free money for users.

(It's a service that captures outbound clicks from your site - apart from giving fancy graphs about those, it then affiliatizes the links across all your affiliate accounts - skimlinks, viglinks, cj, etc)