HiQFMail is a PHP form handler designed with security and flexibility in mind. Configuration is performed outside the form and normally no modification of the PHP source files is required.
Installation is as simple as download, extract source files, edit the configuration files, upload to your server and use. Some Features:
Multiple attachments, Single or Multiple selection from check boxes or lists, Limit types of attachments allowed, Block attachments by extension, Multiple recipients, Select a subset of recipients from a default list, Auto responder and more. PHP4 & PHP5.
While not formally supported some have had success using on Windows.

October 10, 2007 - A problem with some PHP5 installations was discovered where Mail was not being sent. This has been resolved and added to the latest production download.