DirList is a user directory system that runs as a CGI to serve up user lists, search for various user attributes, view their web sites, define personalised user attributes, and keep it all synchronized automatically with the underlying operating system's user database on periodic intervals with cron.
dolt is a cross platform HTML preprocessor, which replaces specially formatted HTML comments with the contents of another file. It works much the same way as SSI, but without the server requirements, as files are processed before they are uploaded to a Web server. For example, it allows you to update a menu on every page by changing one file. This gives you some of the benefits of frames without any of the problems.
Dormando's Oekaki clone is a server software replacement for the popular Japanese Oekaki (draw) picture BBS. This is much easier to set up, runs on a template system for styling, and has a sane codebase to work with for future features. It is fully compatible with all of the old Oekaki applets.
The Download Slave is a very flexible script which is controlled via eMail and stores files requested for downloading on the server's harddisk or sends them via eMail to the user who asked for them. Users are identified by their eMail address and a personal password, so only authorized users can use the service.