Pixelize is a program that will use many scaled down images to try to duplicate, as closely as possible, another image.

Aladin is an interactive software sky atlas allowing the user to visualise digitised astronomical images, to superimpose entries from astronomical catalogues or databases, and to interactively access related data and information from the Simbad database, the VizieR service and other archives for all known sources in the field.

Ping uses ICMP to send out echo requests, and uses the reply packets to calculate latency between the sending and the destination hosts.

Accessible to all, the Debian Administrator's Handbook teaches the essentials to anyone who wants to become an effective and independent Debian GNU/Linux administrator.

Nagios is a host/service/network monitoring and management system.