Yeah, I have to add my vote to Ubuntu as the easiest distro to use. The lecturer for my OS paper at uni taught everything in Ubuntu as well - unless you're taking a second or third level OS paper I doubt they'd expect you to pick up any distro more complex. Fedora/Mandriva/Redhat/SUSE etc. all come in at one tier down from Ubuntu in terms of usability, in my opinion. Personally, I'd avoid SUSE if you're looking to pick up the principals of Linux, since a lot of the software included is quite hacked. Everything from the bootloader to the desktop environment. And then there's the hard to use ones like Slackware and Gentoo.

My favourite distribution of course is Gentoo, but try coordinating an entire class of students trying to install Gentoo for the first time. If the choice were given to me though, I'd recommend Arch, which is kind of like an easy Gentoo. It's easy to use if you want it to be, but it's still flexible and powerful enough to satisfy serious nerds - something you'll find isn't quite as true of Ubuntu.

P.S. I dunno how comfortable you are with Linux installation, but if you want something hassle-free and fast then you might want to check out <a href="http://wubi-installer.org/">Wubi</a>.