This, when used with forms, prevents form automation by scripts and programs by requiring the user to type in a random key. The key is encoded as an image with colors, sizes, random locations and other features making it nearly impossible for an automated program to read.
A complete rewrite from the original. Some of the new features include: separated add/remove list, cookie-based secure login for admin panel, edit/remove user data from with a nice GUI list and user data extraction for printing.
A system which verifies an email address by emailing them a unique ID that must be activated before their information is submitted into the database. Not to be used as a stand-a-lone but used as a snippet when 100% email validity is a must.
A complete mailing list including user add/remove form and administrator emailer. Even though there is a newer version of this script out there, this was posted for sentimental reasons. This would make a great resource to learn from.