How to talk to a USB Device

[Robert Cousins]

Hello:
    I've got several USB devices which I'd like to talk to from a program.
They are Phigets -- a servo controller, an RFID reader, etc.
    Could someone please give me a hint as to the best starting point 
for learning
how to use libusb and the associated facilities? I've been lurking for a 
while on this
list and haven't seen/heard what I think I need to know.

Thanx
Bob Cousins