An experiment with the HTML5 canvas tag and javascript. This generates a random explosion of coloured circles. Based very closely on a script found in the brilliant Foundation ActionScript 3 Animation: Making Things Move!
View the source for the HTML and click here for the JS.
Note: This will only work in compatible browsers. I have been exceptionally lazy and not accounted for incompatible browsers (well it is just a quick test), so if it doesn't work for you sorry! It definitely works in Firefox 3.