Firefox 4 Beta 7 Now Available for Download
So long as you're running Windows or Mac OS X, you'll find that WebGL is enabled by default (you'll also need supported hardware, which doesn't include Intel graphics, at least not yet). Hardware acceleration is one of the next big things in browser development, with the Firefox 4 Beta tapping into Microsoft's DirectX technology.
There's really a laundry list of improvements in general with the Firefox 4 beta, including improved HTML5 forms, support for OpenType font formats, better tab management, and a whole bunch more. Intrigued? If so, give the latest beta release a whirl right here.