For a plug of my friend Thanatermesis' great Debian-based distribution, which recognizes the distro and free-software ethos is not always fully conducive to a positive user experience at the forefront...

http://www.elivecd.org/ - The latest release is always based on Debian Stable and is currently under active development. The whole system is changed in (mostly subtle) ways to make it more attractive to a new Linux user. This is Debian, with some additions. I push this to any friends who say they are interested in Linux, but maybe just want to try it first.

I would not recommend Ubuntu to a new user (unless they were my employee, we use it at work) or Mint for that matter. I would not recommend Debian in spite of using it myself at home, because I don't always want to be the Debian support guy, or have to be the one to say RTFM. Elive tries to be as self-explanatory as possible, even in its somewhat Tarzanic way.