WebDex
Run a fully operational, easy to use internet rolodex site. This script will let you do exactly that. Users signup for your service, opt in to your mailing lists, get an auto generated email upon signup which you can put ads in, and then get their very own little rolodex site. You as admin have full control over the site and all config options. The users have control over adding entries, editing entries, deleting entries, to their own online rolodex.