Exposure Render is the open source GPU volume rendering implementation by Thomas Kroes. What makes this different from all other DVR implementations is the fact that it supports physically-based lighting at interactive speeds. So what does all of that mean? It means that you can make incredibly pretty interactive volume renderings on your own PC. See this youtube movie for example:

… or the rendering below (one of my favourites):

Rendering made at interactive speeds from CT data. Note the pretty shadows!

Read more about Exposure Render by going to its TU Delft Graphics website, or to the Google Code project page where you can download and play with the software!

P.S. Don’t forget to cite the paper when it gets published.