This is a puzzle game in which components need to be combined into a single circuit: connect all computers to a network server, bring water to the taps and so on.

The Uncomplicated FireWall is a front-end for iptables, to make managing a Netfilter firewall easier. It provides a command line interface with syntax similar to OpenBSD's Packet Filter. It is particularly well-suited as a host-based firewall.

Spydr (pronounced like spider) basically is an FITS image viewer. It can work as a stand-alone application but is best integrated in a Yorick-based data-analysis work-flow (Yorick is an interpreted language specialized in numerical computations and scientific graphics). It includes tools to zoom, produce cuts, histograms, Gaussian/Moffat fits, PSF fits (inc. FWHM and Strehl). Can work on single images, sequences of images or data cubes.

AClock is an analog clock with display of smooth seconds. It stays in the dock. The display is customizable:

This program allows you to dump the traffic on a network. tcpdump is able to examine IPv4, ICMPv4, IPv6, ICMPv6, UDP, TCP, SNMP, AFS BGP, RIP, PIM, DVMRP, IGMP, SMB, OSPF, NFS and many other packet types.