Based on Ubuntu but optimized for very old hardware, U-Lite, formerly known as Ubuntulite is a Linux distribution that runs on LXDE, the Lightweight X11 desktop environment. The aim of the U-Lite is to give you a normal desktop functionality out of the box no matter how old your machine is.
The default installation comes bundled with Abiword and Gnumeric for word processing and spreadsheets. It also comes with the Kazehakase web browser and Sylpheed mail client.
The recommended configuration for running the distro is a Pentium 2 machine with 96MB of ram and 4GB of hard drive storage. The installation file for U-Lite is 356MB and can be downloaded via both Torrent and HTTP, though as usual the torrent download is always recommended. If you like Ubuntu but have a very old hardware, then U-Lite is definitely worth a try.