As we're all busy building/testing/rebuilding/QA'ing/etc ... the el7 rc tree, I thought it would be a good idea to also start looking at building the Live media spins (aka CentOS LiveCD/LiveDVD we had for version 5 and 6).
The first thing was to rebuild the needed tools but that was easy to do (you can find the needed tools for the time being on http://people.centos.org/arrfab/CentOS7/LiveMedia/RPMS/ , but those will appear later in the Extras repository when there will be an official CentOS 7 tree on all mirrors). I decided to take another route for the C7 live spins. First point is the fact that with Gnome3, it was quite difficult to produce an iso file that could fit on a CD, but I did it : it's just a basic Gnome3 desktop (with the Classic theme) and the only application that I was really able to put (after having removed some other smallers apps/fonts packages) was Firefox. I guess it's a good candidate for people wanting to test "live" what CentOS 7 can be (and obviously it can still be installed on the hard disk, thanks to anaconda/liveinst.
Instead of having a bigger DVD containing both Gnome and KDE, I thought that splitting those into two smaller variants would be better, so that people don't have to download a bigger ISO file , testing something they don't want, and worst, installing on disk something they don't want to use (aka KDE vs Gnome).
If you're interested in the tools/kickstarts used to produce those live media spins (still be to really built when CentOS 7 Final will appear , so be patient ...), you can find it on the official git repository used by the CentOS Project : https://git.centos.org/summary/sig-core!livemedia.git or you can also fork/clone (and why not create a Pull Request on Github if you want to contribute !) : https://github.com/CentOS/sig-core-livemedia