Some time ago I checked the state of WebGL and it looked not too great. This changed dramatically recently, so I dare to say that the next browser generation coming up will change the 3D capabilities of the web this year. In the current generation (as of January 2011) there is no regular browser WebGL enabled.
Consequently, to see any WebGL demo you need a so-called nightly build. Here’s a webpage that describes where you can get nightly builds of browsers that already support WebGL (namely Webkit/Safari, Firefox and Chrome).
For Blender users, GLGE might be the path to take.
Also the Google Code WebGL samples are worth a look, featuring the Aquarium example that sports a winning software combination IMHO, that might make web3d finally arrive in 2011: