Microsoft serial mouse
Mouse Systems serial mouse
Logitech Mouseman serial mouse
Logitech serial mouse
ATI XL Inport busmouse
C&T 82C710 (QuickPort) (Toshiba, TI Travelmate)
PS/2 (auxiliary device) mouse
Touchpad devices like Alps Glidepoint also work, so long they're compatible with another mouse protocol.
Newer Logitech mice (except the Mouseman) use the Microsoft protocol and all three buttons do work. Eventhough Microsoft's mice have only two buttons, the protocol allows three buttons.
The mouse port on the ATI Graphics Ultra and Ultra Pro use the Logitech busmouse protocol. (See the Busmouse HOWTO for details.)