I have a USB stack that works in host mode you can use -- you'll need to add the upper level logic for handling HID (I talk SBC/SCSI)...
You can see all the code at the bottom of this page in the skeleton project: http://www.cpustick.com/downloads.htm
usb.[ch] is the USB host/device mode driver, and scsi.[ch] shows how to put an upper level SBC/SCSI driver on top of it.
Unfortunately, you'll have to ignore #if's for all the other MCUs -- but the 52259 works fine.
I've also used the code to talk PIMA, so it should be pretty flexible.
-- Rich (rich@testardi.com)