Browsing around the net as I do and found this site at
Techspot . It is basically a review on 3 ergonomical rodents for those who care about how they communicate with their PC.

This one really grabbed my attention by the way in which you hold the mouse is completely different than normal. From the review above, it is also very easy to learn how to use it.
As you can see from the animation it kind of clips on to you hand, you operate it via a tracker ball.
The only downside of this mouse is that it's kind expensive ($130)(
see for US prices )
If that's too pricy you can get a good laser mouse chez logitech.