Pantheon

This is Pantheon, running on Ubuntu 11.04. Pantheon is a new desktop environment designed by the Elementary OS team that will run on Ubuntu. It's similar in form to Unity, but uses much less memory. It consists of three new desktop apps: Plank, Slingshot, and Wingpanel.

You can see two of those programs in my screenshot. The top taskbar which has the clock in the middle is the Wingpanel.
The Apps menu on the left side of the Wingpanel expands into the Slingshot menu (more screenshots later hopefully).

Pantheon was touted as being the first user-friendly environment for advanced 11.04 users. "Unlike other "all-in-one" environments, such as GNOME-Shell or Unity, Pantheon was made to be modular and lightweight. Don’t like the launcher? Replace it was something else. Hate the file browser? No problem. With Pantheon you are able to replace any piece you want with something else." [link]

And that's exactly what I did! I replaced the Plank dock with Docky because Plank was just a little too simple and occasionally misplaced my windows or failed to show an active window on the plank. Plank is currently an unstable alpha, so I won't blame it... but I needed something a little more reliable.

Docky is better about showing all the active windows, and it comes with a few very useful plugins as well.

For example, one concern that some users have expressed is that there is no way to access the file manager on Pantheon. Well, there is... but it, like Pantheon, takes a little getting used to. The Marlin File Manager showed up in the Pantheon list of programs, and it is a wonderful file manager. However, nothing beats having shortcuts to your favorite places... and I accomplished this with Docky. Docky also uses the default file manager Nautilus which I do prefer using over Marlin.

All in all, I like my new desktop. And it is using about 1/5 the amount of memory that Unity was using. Very lightweight indeed!