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.
Gaby is a small personal database manager using GTK+ and GNOME (if available) for its GUI. It was designed to provide straight-forward access to the types of databases a casual user would normally use, while keeping the ability to easily create databases for other needs. It was designed with extensibility in mind and relies heavily on plug-ins.
The Information System Development Kit gives the developer a platform-independent method of creating Information Systems with data forms, SQL database access, database-browsing support, report generator and many other useful features. ISDK is now in a development stage and it is available only for the Linux operating system. The form module now works on text terminals using the ncurses library (not functional right now), and on the X-Window system using the GTK+ toolkit.
dteq is a query tool that passes results through a template. It is well-suited for auto-generating all kinds of things from a database like authentication tables, DNS zone files, or whatever you can come up with. It also does updating commands like INSERT and UPDATE and reports back the number of rows affected. This used to be named mysqlquery but it is now DB-independent, with cdb, MySQL, and PostgreSQL drivers available.