This is a library for MAX3421E-based USB Host Shield for Arduino -> http://www.circuitsathome.com/arduino_usb_host_shield_projects
More information can be found at http://www.circuitsathome.com
The development of this project has been discontinued. Current revision of the code can be found at https://github.com/felis/USB_Host_Shield_2.0
I have added compatibility for old Sparkfun USB Host shield which had the pins swapped. To use this library with the old shield refer to this blog post for instructions.