Motorola Mobility software developer Brandon Jones has ported the 2Fort map from Team Fortress 2 over to WebGL, which runs without plug-ins in a compatible browser.
In the video demonstration posted below, Jones clearly points out that the conversion isn't perfect: it's missing normal mapping on brush surfaces, water, accurate lighting, surface displacement, and a 3D skybox. It's also not playable, but at this point, he's just happy to successfully port Valve's Source Engine over to WebGL.
According to Jones, the map is running a smooth 60fps in most cases, and even jumps up into 100fps -- it just may not look like 60fps in the video due to his capture software. Still, don't expect to play Team Fortress 2 via WebGL anytime soon, as this map alone uses 200 MB of assets that must be downloaded to the browser. No web server will want to host something of that size to be downloaded thousands of times a day, especially since it's just a test and not something profitable (yet).
Of course, because the content is owned by Valve Software, Jones will not be making a live demo of the map even if he did have the allotted bandwidth. As it stands now, he's providing the code on GitHub. That said, perhaps if an entire team could be put together to get Valve's Source completely up and running in WebGL, the studio might green light porting Team Fortress 2 over to the browser. What better why to reach out to a wider audience with your free-to-play shooter?