CGI::ContactForm is a Perl module that generates a contact form for the Web and sends a message to a predestinated recipient. Unlike many form-to-mail programs, it's limited to this single purpose, but it allows you to set up a decently designed form with a minimum of effort. In other words, it's simple to use rather than flexible, even if there are quite a few customization possibilities.
Gutuma is a feature rich PHP newsletter/mailing list management tool that is designed to be easy to install and use. It doesn't require a database, yet offers multiple lists, import and export from CSV, file attachments, drafts, AJAX subscribe gadgets, administrator email notifications, MD5 protected logins, and batched deliveries that can be driven by a cron job.
sendPGPMail.cgi is a small CGI script for sending an encrypted PGP email message to a predefined receiver from an HTTPS secured Web page. The typical use of this script is to provide the users of a secure Web site the possibility to send a secure email to a predefined employee of a company. The CGI script gets its input from an HTML form and passes it on to gpg. The message and its attachments are encrypted using the PGP public key of the predefined receiver.
Zoop is an object oriented framework based on a front controller. It is designed to be very fast and efficient and very nice for the programmer to work with. It is easily extensible, and you need only include the functionality you use. It features GuiControls (a PHP implementation of .net's webcontrols), AJAX support and integration, automatic form validation and creation (including db integration), a Smarty templating system, PDF creation, session handling, and SMTP template-based email sending.