The default for CORE images
A fork of the GNOME2 desktop, replacing KDE as the default for LARGE images due to better stability in the chroot jail. Mate is not yet available for Debian-based distros on armhf architecture.
The Ubuntu Unity desktop; only available with the Ubuntu 12.04 LTS LARGE image. Unity2D is no longer under development by Canonical; consequently not available in Ubuntu 12.10 and up.
E17 is a lightweight window manager that also provides many of the features of more resource intensive desktop environments. As such, Enlightenment straddles the line between the two. The default desktop for Bodhi Linux.