Taken from

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

Removed all but the first image, then linked to the screenshots on the offical site, after a suggestion from Crispy.
Wow. That is cool. The really interesting part is that they're eventually planning to embed webpages into Second Life using this technology. Crazy stuff!

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.
Yeah, OpenGL rocks. I was playing with compiz(An openGL based window manager for Linux) and was stretching my browser around while watching some stuff on

These where playing live at full speed with audio. No problems at all. This is just more proof of concent, however. I would really love to see SL's implementation of it. They have been talking about it for a long time, but this is the first time I have seen it in action. They already have streaming QuickTime movies in game, on textures, so you can move around and have to warp, with no added delay or FPS harmed. My idea: A tablet PC held in the hand of the player, which cordinates with a HUD of the tablet PC for surfing around the web, and letting everyone see what you are surfing.

It works! And doesn't do a bad job. I am making this post from it right now. I would suggest you all try it out.