Dr Destruct-o takes apart a couple of Microsoft Explorer Optical "IntelleMice", to see if there are any useful goodies inside.
Step 1: Here We Have a Couple of Still-together Mice
These seem to show up with some regularity in the E-waste bins at work. I don't know if the Microsoft mice are more prone to failure than other mice, but they're certainly more recognizable in the waste bin.
One of these says "version 3" on the bottom sticker, and the other doesn't. They're USB mice, although apparently they'll talk PS2 as well, using a merely physical adapter (these adapters don't actually translate between PS2 and USB protocols, they just connect the wires differently. The processor inside the mouse detects which kind of connection is in use, and reconfigures its pins as appropriate.)