Knoppix

The ideal Linux distribution for newbies - in that it runs from a CD, doesn't write to a hard disk (unless you opt to install it on a hard disk later on) and detects most hardware automatically.

Comes with a fully featured desktop and word processor etc.

See http://www.knoppix.org

Knoppix is KDE based, whereas others exist for e.g Gnome (e.g. gnoppix?)