Even more fun than Ubuntu (to my mind) is
Knoppix...
http://www.knoppix.net/
It's a complete distro in a single CD, designed to run from the CD, though you can install it to a HD partition if you want. Using high compression, they can get close to a gigabyte of software onto the CD. And there is a DVD version as well, with a truly huge amount of stuff. They have torrents so you can even download it on dialup, though I can't imagine anyone nuts enough to download the DVD on dialup.
