The logitech Marble trackball is layed out more like a traditional mouse with the trackball located in the center.
It also has scroll buttons located on either side above the two main buttons. The Marble is suitable for both left and right handed users aswell as being compatible with PC and Mac. The forward center position of the trackball also allows it to be operated with one finger if preffered.

Another great feature of this mouse is the price! Compared to many trackballs it is relatively cheap, but dont mistake this for poor quality as this mouse will serve you well, and reduce the strain put on your hands and wrists by traditional mice.

The lack of buttons seem to be the only downside to this trackball, but this may only be a problem if you are used to having a mouse with three buttons or more.