Over the weekend, I spent a few hours putting together a jquery script that allows for mouse detection over a 10 x 10 grid. I then placed an image over a 10x10 grid, as the mouse moves to different parts of the grid, different images appear. A demo of this can be viewed here. Take a look at the source code on the page to see it in action.
This is the portion of the code doing the main work:
And you can grab this code from my gist.