...back in 2001, I used Double-Choco-Latte at a job. Free, integrates with multiple databases on the back-end. On Debian, it's as simple as apt-get install dcl. Back in the day, it was written in PHP. No idea what it's doing these days. It was über-configurable as well, provided you had some skill with PHP (and it also had an admin section whereby you could do some basic and even intermediate configuration without knowing PHP.)