Ed showed me this great index of a million mailing lists This site has indexed just about every open-source mailing list out there.
Its searchable too! It came in a big help when researching the Pear class LiveUser which is a really neat Authentication and Permissions package for PHP.
The only problem is that you gotta do some major hackage to make it use something besides XML, DB, or MDB as backends. I’m currently in the process of figuring out how the experimental Pear_Auth plugin works so I can make it use passwd style files as authentication backends :D