Windows only: TeamPlayer allows you to use multiple mice and keyboards on a Windows based system. Under normal circumstances you can plug multiple USB mice in, but moving the two simultaneously will result in Windows struggling to decide which input to use for the single cursor on the screen. TeamPlayer is designed for a group environment where multiple people will be interacting with the same computer. Each mouse is assigned a unique coloured cursor to identify it. When testing on my system my primary PS/2 mouse was assigned red, and the secondary USB mouse was assigned blue. There are two small caveats with Teamplayer:
It appears to handle the problem of multiple mice by shifting the focus to the "real" windows cursor for actual actions. For example if you attempt to close two windows simultaneously with two mice you can see how TeamPlayer activates and inactivates the cursors as the command is executed. Under normal circumstances it shouldn't present much of an issue. The other issue that popped up: on my triple monitor setup TeamPlayer locked the cursors to the middle and right monitor, leaving the left one out in the cold. This should present even less of an issue, given that in most situations TeamPlayer will be used by multiple users it will be with a larger monitor or a projector. TeamPlayer is Windows only, free for non-commercial and personal use, commercial licenses start at $US196 for three users. Thanks Jason!