I created some fairly short screencasts showing off GNOME, XFCE and KDE on Fedora 18. This was primarily to show students in a class I'm doing the basics of each desktop and some of the common customizations I prefer to make but I thought I'd share them more widely. The were done using a SPICE connection to a remote KVM virtual machine and recorded on my local system with qt-recordMyDesktop. Then I used ffmpeg to convert them from ogv to webm.
Please note that microphone I used sucks and has a lot of background hiss. I have a better microphone coming for future videos but if anyone wants to do some Audacity filtering magic on them to clean them up, be my guest. They are 1280x800 in size and in webm format. I've embedded the GNOME one and provide links to the others below. Enjoy!
I may do a few more... for MATE, Cinnamon, and LXDE but I haven't done them yet.