Ubuntu Light is a simplified version of Ubuntu available to PC OEMS. It uses an early version of Unity and focuses on getting end users booted and online as quickly as possible.
From Canonical's site:
Ubuntu Light, powered by Unity, is a simplified version of Ubuntu. It's perfect as a companion to Windows for a fast web experience or as a standalone operating system for use in mobile or embedded devices. Typical startup times are seven seconds on a device with a solid state disk drive (SSD). Boot times can extend up to 20 seconds on hard disk drive (HDD) machines. PC OEMs can get Ubuntu Light now. Contact Canonical for more details. You can also test Unity on Ubuntu 10.04 LTS now.
A PDF datasheet containing more detail about Ubuntu Light is available here.
