• KNOPPIX

From author's site:

KNOPPIX is a bootable Live system on CD or DVD, consisting of a representative collection of GNU/Linux software, automatic hardware detection, and support for many graphics cards, sound cards, SCSI and USB devices and other peripherals.

KNOPPIX can be used as a productive Linux system for the desktop, educational CD, rescue system, or adapted and used as a platform for commercial software product demos. It is not necessary to install anything on a hard disk.

Due to on-the-fly decompression, the CD can have up to 2 GB of executable software installed on it (over 8GB on the DVD "Maxi" edition).