Pinot
Version 0.30 - Linux - GPL
More information here.

Usermon
Version 1.3.3 - Linux - GPL
Screenshot
Usermon is a GAI-based applet. As such, it works with all the desktop environments supported by the GAI library, ie GNOME 2 and WindowMaker.
It monitors who is logged in on the system periodically and raises an alarm when the number of users reaches a limit. The limit, the alarm and other parameters are configurable.
GAI 0.5.10 is required. Fedora Core users may install the package included in Fedora Extras.
Download Usermon : source tarball, source RPM, binary RPM for Fedora Core 4/i386

MultiDisplay
Version 1.10a - AmigaOS 3.x - Freeware (no longer maintained)
Screenshot, Readme
I wrote MultiDisplay a few years ago when I had my Amiga 1200. It uses the datatypes library to find out the file type (binary, text, archives, pictures... ) and call a user-defined program.
The archive contains the hypertext documentation (AmigaGuide format) in French and English.
Version 1.10 can also be found on any Aminet mirror site. Version 1.8 was published on the Aminet 22 and Aminet Set 6 CDROMs by Stefan Ossowski's Schatztruhe.
Download Multidisplay : source and binary