Attaching USB devices to Nokia Internet Tablets
To use a Nokia N800 (and most likely the N810) with OS2008 as a USB host you will first need an appropriate cable or adaptor. I use a L19BT 'USB A (female) to USB A (female)' from Maplin.
To activate host mode as root issue the commands
# echo host > /sys/devices/platform/musb_hdrc/mode
To restore peripheral mode issue the command
$ sudo gainroot
and before you can do that the device needs to be in R&D mode, or the gainroot script modified - for which you'll first need to be in R&D mode :-)
More information can be found on these sites