Cinnamon desktop is a fork of Gnome three that aims to maintain a Gnome 2-ish like look. Its a good desktop for people who hate Gnome shell and find it a mess. The Cinnamon desktop is maintained by the Linux Mint team and is the default desktop for that distro.
Cinnamon is undergoing heavy development as its nearing 1.6 release. Users may like to test the distro and report bugs to the developers. To install the latest Cinnamon desktop in Ubuntu, add a PPA by running these commands in terminal:
sudo add-apt-repository ppa:gwendal-lebihan-dev/cinnamon-stable
sudo apt-get update
sudo apt-get install cinnamon