Don't forget Lubuntu. The LXDE variant of Ubuntu is, in my opinion, and under-appreciated distro. The stability and community support of Ubuntu, with the speed of the lightweight LXDE and without that distracting Unity stuff. For older PCs or machines with modest specs, this has repeatedly been my distro of choice. 13.10 added Zram for the live CD too, which will help with low spec machines.
By the way, Lubuntu is a good choice for former windows users because of the familiar taskbar, window, and menu layout. I never did get used to having the buttons on the left when I used Ubuntu.