Our Freeduino USB Host boards are in production.  The board is 100% Arduino (TM) compatible including all the quirks of the Arduino (TM) form factor. In the service of total disclosure, we had to zap one mounting hole that is normally above the ICSP header, to accomodate some parts. They look sharp.

Our board was inspired by the boards that Google spun and presented at the Google-IO conference a few weeks ago. Our board is somewhat smaller, and we felt more in tune with what the experimenter and hacker market would want.  The board has a linear regulator rated for 1.5 amps to provide enough power to be able to charge your cell phone, and still have some fun with your Arduino (TM). It will connect with any Android phone with the new "accessory mode" firmware. In addition it will connect with almost any other USB accessory such as thumb drives, keyboards, mice. This will be a step forward for Arduino (TM) - compatible connectivity to more juicy devices. Arduino mouse and keyboard library anyone?

Freeduino USB Host Boards are in stock in shipping, orders over a dozen pieces may require up to two day to ship. To connect the board to your Android phone you will need a Micro-USB connector cable.

Here's a video teaser of a project Modern Device customer Joshua Oster-Morris put together in six hours. Too bad the board is mostly hidden by a Sparkfun shield. 

Here's another minimal proveout of the Freeduino board on a Galaxy Tab 10.

Specifications:

• 1.5A linear regulator for external power jack
• 6-9 volts external power, with 6 volts being ideal.
• Power negotiation with USB
• USB hosting via MAX3421 chip
• Arduino (TM) UNO form factor minus one mounting hole
• Uno Bootloader (Optiboot) and Arduino Boards Menu setting
• board size 3.4" x 2.1"
• white boards, black silkscreen
  
• CC share alike / open hardware license 
  

Resources:  

• Freeduino Host Board Current Schematic (pdf)
  
• Freeduino Host Board Current Eagle Files 
• Instructions and libraries on the Modern Device Wiki