Web-B-Mail
A very simple Web-based messaging system. Only registered users can mail other registered users, thus cutting out spam. You can let your users upload their own pictures, or allow only the admin to do so. Messages stay on the website, but can send regular email notifications when a user gets a Web-B-Mail message. It was originally intended for use by online classes or classes of small children for whom Internet email access might be inadvisable, but has also been used by dating services and other small communities to keep communications out of "regular" email and limited to the site.