Someone mentioned modifying the N800 cable by prying up the mini-B connector on the stock cable. I'd like to report it also works with adapters (mini-b to female-A), however I recommend using needlenose pliers and a careful hand to control bending the side, and to scrape the plastic back over the half you will need to lift up.

My successful attempt used a silver conductive pen: http://webtronics.stores.yahoo.net/simicopen8.html where I squeezed out a drop of ink and used a needle to apply it between pins 4 and 5.

One warning - you want to keep whatever you use to short the lines way back so you don't damage what it gets plugged into, and you want to be careful to restore the case to the right shape for the same reason.

Looking into the 5 pin mini B, with the shorter face of the trapezoid facing up, pins 4 and 5 are on the right, so you need to grab that side and twist it until you can easily get at the base of the pins. Then either solder or use conductive ink to bridge them all the way in the back. Then bend the casing back.

Note: try not to short the ground (pin 5) and the case - it shouldn't really hurt, but to be technical it shouldn't be done either.

This works with an unaltered micro to mini B adapter (see the n810 host mode made easy), and with the n800 - the tiny USB microSD adapter I have was recognized in both as host with this.