This WordPress plug-in was created to modify and create links in posts. Right now it does two things; adds affiliate information to existing links. The affiliate information is added after the links are created, so those are modified too.
When adding affiliate information, you need to know the HTML query to add to links. Most sites give you things like affil=username to append to the URL that tells them who referred the visitor.
You can also convert certain keywords like “Yahoo!” to Yahoo!. Currently they keyword search is case sensitive, and you have to prepend http:// to the links.