There is a library for the Max3421 that I have used with a USB Host shield. If the attached device is HID compliant, the library and shield work out of the box. At least they work for me with a USB keyboard. They also work with a USB mouse.
I think that writing actual device drivers to reside on an Arduino would be an adventure. I won't predict how difficult I think it might be, and I certainly wouldn't say that it can't be done.
Here's the board I am using: http://www.sparkfun.com/products/9628
I downloaded the library from here: https://github.com/felis/USB_Host_Shield
Here's a page with some projects: http://www.circuitsathome.com/arduino_usb_host_shield_projects
Good luck! I hope you keep us informed.
An unexpected bonus from this shield and library (at least I didn't see it coming):
The '3421 has eight general purpose input pins and eight general purpose output pins that are brought out to pads on the shield.
It is possible to use some of these pins to interface to common text LCD display (HD44780 controller without using any more Arduino pins (other than the SPI port interface pins to the '3421). How cool is that?
There is an example sketch in the MAX3421 library directory that shows how it's done. In fact, my specific application was with a 19-key USB keypad and a 20x2 LCD. All of the interface stuff was already done for me!