I generally try to avoid tinkering too much with the insides of WordPress, but if I did I would read Devlounges How to Write a WordPress Plugin first. It’s even available as a nicely downloadable PDF.

Yesterday I needed to delve into Arne Brachhold’s Del.icio.us plugin to figure out how to add proper titles for links from main or archive pages. It was a dirty hack, but I got it working somehow. If you need to know, it involved hacking his Javascript and I’d be happy to share if you ask.