This is a demonstration of terrain generation using the diamond square algorithm.
You can see it in operation on my blog. There's also some nice documentation available.
You'll need CoffeeScript installed, but then it should be as simple as:
cake build
This should create a directory 'lib/' with the compiled .js in it. Then you can open index.html and it should draw a starting grid on the canvas.
Let me know if it isn't that simple.
I've tested it in Safari, Chrome and Firefox.