http://www.thinstation.org/

Thinstation allow you to turn a normal desktop into a thin client, or at least something that has the functionality of a thin client. You definitely wouldn’t get the power savings you would with a real thin client, but it may be worth considering for testing forms of VDI.

One of my coworkers runs a linux lab. Many of the PCs in the lab are nearing the end of their three year cycle. It would be possible to setup a linux terminal server, install Thinstation, and point the Thinstation clients to the terminal server. Then if/when the computers die, they could just be replaced with another low end computer or a thin client. The thin client would be idea for power savings though.

Thinstation also supports RDP, Citrix, and a ton of other protocols. I have not tried the multimedia experience in Thinstation though.