Hoppy's Balloon 3 USB Breakout board
This breakout board connects to J12 (for USB slave, console and power) and J13 (for USB OTG/host and auxiliary serial ports COM1 and COM2) of the Balloon 3 board. As it stands at the moment (28 September 2007) a couple of modifications are needed to make it useful.
USB host still isn't working, but that's mostly because the OTG transceiver on Balloon 3 isn't yet understood by the kernel.