USB Host Mode
External vbus power is easy:
Connect your type A (with ID-pin shorted) microUSB to USB cable into webOS. Plug the data leg of USB-Y cable (usually found with 2.5" external HDD enclosures and such) into this cable. Plug the root of the Y cable into a hub or whatever device you plan to use. Plug the "power" leg of the Y cable into some powered usb socket be it a powered hub, a PC or whatever. Enjoy your usb device.
Example of cable that will work: http://www.ebay.com/itm/High-Quality-micro-USB-USB-Female-Cable-USB-OTG-N900-/170687828639?pt=PDA_Accessories&hash=item27bdc9929f Search for OTG cable on eBay and thee are plenty.
The USB-ID should be 1-1
If you get a error like this in dmesg:
usb 1-1: rejected 1 configuration due to insufficient available bus power
This command got me past this error:
echo 1 > /sys/bus/usb/devices/1-1/bConfigurationValue
This worked for me and hopefully it can be of use to someone