The Embedded Debian Project is making Debian GNU/Linux a mainstream choice for embedded projects.
Emdebian 1.0 will be released based on Debian 5.0 "Lenny" but will only be available for one architecture (ARM) and in one flavour (a mix of what will become the flavours described below). Emdebian 2.0 (based on Debian 6.0 "Squeeze") will support the concept of flavours of Emdebian as well as a wider range of architectures.
Embedded Debian @ Debian Wiki
Making Embedded Debian
LinuxDevices.com : All About Linux-powered Devices