Capabilities of Expansion Boards for Gumstix Overo Computers-on-Modules (COMs)

Board	Price	Sufficient power and USB serial console to make COM usable?
Thumbo	$27.50	No: (not enough) USB power only
Pinto	$27.50	No: now USB serial console
Summit	$49.00	Yes: power connector & USB serial console, HDMI
Palo35	$59.00	Yes: power connector & mini-USB console, 3.5" LCD touchscreen-capable & accelerometer
Palo43	$59.00	Yes: power connector & mini-USB console, 4.3" LCD touchscreen-capable
Tobi	$69.00	Yes: power connector & USB serial console, HDMI & ethernet
Caspa VL	$75.00	No: neither power nor console, wide-VGA camera with IR filter
Caspa FS	$75.00	No: neither power nor console, wide-VGA camera w/o IR filter
Tobi-Duo	$79.00	No: power but no USB serial console, two ethernet ports
Chestnut43	$79.00	Yes: power connector & mini-USB console, 4.3" LCD touchscreen-capable & ethernet
Gallop43	$129.00	Yes: power connector & mini-USB console, 4.3 LCD touchscreen-capable plus GPS and accelerometer
Stagecoach	$229.00	Different purpose: for connecting multiple COMS together

Keyboard and mouse must be connected to the expansion board via the USB OTG mini-B connector, not the mini-A's, one of which is for the serial console. The hubs I see have output, host-side connectors that are mini-A. Therefore, you will likely need either a mini-A/mini-B cable or some adapters. As of this writing, mini-A/mini-B cables are a bit hard to find even in Silicon Valley. Do yourself a favor and order one when you buy your Gumstix!
You must use a powered USB hub.