SafeListPro
This script directly emulates those sites like pro-safelist.com. It is a feature packed full site program with everything needed to fully or partially automate this type of site and comes with paypal billing module built into it. All aspects of this type site are covered in the program including a lost password/username retrieval tool. Admin can set it up to be fully automated or he can opt to validate new users manually if he so chooses. The script has many configurable options such as automated mails to user and admin.