http://noteslate.com/ The noteslate is definitely what you're looking for. But I'm not sure it is released at the moment.

All the following benchmarks were done with Ubuntu 11.04 32 bits on a Dell Latitude D510 Intel Pentium M 1.60 GHz with 768 MB RAM, Intel Graphics, no proprietary drivers. Gnome Shell comes from the Ubuntu Gnome 3Team PPA. Unity and Gnome Classic uses Gnome 2.32. Gnome Classic uses metacity; compiz is disabled. I used the same applications for each : Firefox, Gnome Terminal, Nautilus. After Clean Boot Unity : 155.18 MB Gnome Shell : 125.09 MB Gnome Classic : 143.86 MB Application set 1 (as seen in the original article) : Unity : 254.69 MB Gnome Shell : 232.78 MB Gnome Classic : 245.26 MB