maemo.org - Talk - N800 USB 2.0 HUB (direct connect)

It's pretty straight forward:
1) Get cable with MiniUSB on one end. Chop cable in half.
2) Get cable with full female A on one end. Chop cable in half.
3) Join cables together colour for colour (cut cables to make desired final size) using solder and heat shrink/B-Connectors/Electrical tape (depending on your level of expertise and available materials).
4) Plug in and enjoy. Use the USB Control package to switch between host/client through software, or
4b) Bend open miniB connector, short pins 4+5 using a tiny dab of solder or some other conducting material, and fold connector closed again. This will cause the tablet to automatically switch into host mode when the cable is connected.

Alternatively if you wait a day or two and keep an eye on the forums I'm going to be offering pre-OTG'd mini-B pigtails (one end's the miniB described in 4b, the other end is just the wires) that you can cut/join it onto whatever you like.

Thanks!
-Rob