Knoppix - (Debian ofspring) Run live from CD, da best auto hardware detection system, 2 different browsers, email, OpenOffice, K3b CD burning software, XMMS player, and much more software (total of 2 GB of apps compress to fit a CD).
Damn Small Linux - (Knoppix ofspring) live CD with Links & Mozilla Firebird browser, XMMS, Rdesktop, Monkey Web Server, and much more. It makes an excellent system diagnostic tool or terminal boot disk for thin clients, and all of that fit into 50 Megs.
Gnoppix - (Knoppix/Morphix ofspring) a weaker variant of Knoppix that borrowed some of the idea from Morphix and use Gnome instead of KDE.
Mandrake ? Low learning curve for Windows user, with excellent documentations.
Red Hat ? Almost as easy to use & learn as Mandrake.
SUSE ? I found that it is slightly easier & nicer than Red Hat, however it cost money.