First there is the SlimBlade Media Mouse, a laser mouse that also has media playback controls, like volume, play/pause, and next/previous. There is also a navigation pad and a 360 degree scroll ball, ala the BlackBerry Pearl if I had to guess.
Then the SlimBlade Presenter Mouse which has two major features, first the 4-way tilt scroll. Then there is the small USB receiver that tucks away inside the mouse itself. This mouse is also available in two colors, deep blue and ice blue.
The next logical step is to combine those two, and they did, with the SlimBlade Presenter Media Mouse which has the scrolling ball, and the nav pad. It apparently retains all the other features of the presenter mouse though.
The last addition to the Kensington line is the SlimBlade Trackball Mouse which has the scroll ball, Bluetooth connectivity, and a battery level light. The four mice are available now I presume, and are priced, in order of mention, as follows: $59.99 for the Media Mouse, $49.99 for the Presenter Mouse, $79.99 for the Presenter Media Mouse, and $99.99 for the Trackball Mouse.