This web app can be used to test Micromouse algorithms in your web browser. It exposes a JavaScript Mouse API for controlling a simulated mouse running in a simulated maze. You can type your mouse driver code directly in a textbox on the web page. There are a large number of mazes to test your mouse algorithm . These mazes have been used in Micromouse competitions. The source of these mazes are http://www.tcp4me.com/mmr/mazes/
You can try the Micromouse Simulator online
This applicaiton is all client side JavaScript. The best bet might be to download and run it locally. This way you can edit and save your mouse driver code locally. It is also helpful to use Firefox's Firebug extension for debugging.