I had a quick look at the processor used in the reciever for my wireless mouse and that has what looks like a micro which is very similar to 8052 although not code compatable and a usb/ps/2 serial interface unit.its a cypress CY7C63722.
Also you will find a usb design suitable for a fpga rather than a cpld at www.opencores.org i cannot comment on it as i havent even looked at it.