I asked that same question, no one will answer it. It is all a matter of opinion. You could go to
http://www.distrowatch.com or
http://www.linuxiso.org . What kind of distro do you want? Live CD, Source based, desktop, minimalist...
Live CDs:----------------Source based:-----------Desktop:
-----------------------------------------------------------------------
Knoppix -----------------Gentoo--------------------Mandrake
Morphix -----------------Sorcerer-------------------Slackware
Jollix---------------------Source Mage--------------Lycoris
PLD Live--------------------------------------------Suse
Mandrake Move-------------------------------------RedHat
XoL ------------------------------------------------Fedora
NavynOS
Slax
It just goes on there are over a thousand linux distros. It all comes down to what you like...