Introduction:
uBrowser is a simple Web Browser that illustrates one way of embedding the Mozilla® Gecko rendering engine into a standalone application using LibXUL. In this case, the contents of the page is grabbed as it's being rendered and displayed as a texture on some geometry using OpenGL™. You are able to interact with the page (mostly) normally and visit (almost) any site that works correctly with Firefox® 1.5.
Its purpose is to provide a test bed and a proof of concept for the software I'm working on at Linden Lab. By releasing the source code I'm hoping that others can benefit from what I've learnt as well as help fix bugs and identify areas for improvement. It is not meant as a replacement for your regular 2D browser.

More here
*Edit*
Removed all but the first image, then linked to the screenshots on the offical site, after a suggestion from Crispy.
You really should just link to the screenshots page though, rather than hotlinking and displaying all of the images inline. Yeah, I know you had a warning, but still.