BusyBox

Busybox is a program with small memory footprint, designed to replace a suite of otherwise large Linux utilities. It is commonly used in embedded Linux systems.

Over 58 projects are listed on the busybox projects page.

See http://www.busybox.net/

A good article on busybox is at: http://www-128.ibm.com/developerworks/linux/library/l-busybox/