This past weekend I picked up the new Wireless Notebook Optical Mouse. This thing is very cool. Has a little wireless transceiver that attaches to the mouse and turns off the optical part so you can transport it.
Another recent discovery is that IntelliPoint 5.2 added back functionality that shipped a year or so ago but was subsequently removed. You can now customize the mouse hardware buttons on a per application basis. One customization I make is I hardwire the back button to delete messages in Outlook, and the forward button to space through messages for reading in the preview pane. It lets me drive outlook for a long time w/o touching the keyboard ;-).