Few hours ago, Ubuntu developers blog announced the availability of Ubuntu 12.10 (code named ‘Quantal Quetzal’) Alpha 3. It comes with the Kernel 3.5, Firefox 15 Beta, LibreOffice 3.6 RC1, Gnome Shell 3.5.4 (including revamped ‘Nautilus’ with UI changes, which still looks a bit ugly due to Ubuntu’s theme incompatibilities), Xorg 1.12 and more.
Simultaneous to this, Kubuntu, Xubuntu and Lubuntu have also released their Alpha 3 versions as well. Please remember that 12.10 hasn’t even reached the ‘Beta’ stages yet, so if you want to try it out, then use it with extreme caution as it should contain bugs (guaranteed! ;-)).
If you want to get more information on how to download the ISO disk images, then please visit this page. Good luck.