Ubuntu is kind of the standard choice for starting with linux, but there is a few other that offers the same type of experience : Mint, OpenSuse, kubuntu, fedora, mandriva... (uncomplete list).

Each of them has it own specifics but at the end of the day they are all built around the same software. A criterion of choice may be the desktop offered as default : Gnome or KDE. Anyway in almost any linux desktop distribution you can change that also.

Then there is some distribution more excentric that stands out of the crowd, but may not fit your need :

- debian : very stable, strong community spirit. Personnally I'm using for servers only because their conservative software updates on the desktop doesn't suit me.

- Arch linux : always the newer packages, user-friendly to the advanced user but definitely not to the newbie. I just love it !

- Gentoo : if you love the noise of your processor compiling... for advanced users also.