I remember building something similar for a class project as part of my undergrad degree. It was basically a website where you could sign up for a virtual desktop and use the nx protocol (https://www.nomachine.com/) web browser plugin (it felt like there was no latency) to view the remote desktop. We supported Ubuntu Gutsy and Windows XP SP2. It worked great on those little Eee things that were popular at the time -- access to a desktop environment with a quad core on an Eee.

This was around 2007-2008 or so, so it's tough to find anything that still remains from the project -- we sucked at marketing and didn't really get a userbase, so it died off.

Here's a few docs from it that still remain online: http://www.cis.temple.edu/~wolfgang/c4339s08/WebDesc/