After testing my MintyBoost on all things iOS in my house I ventured over to a couple other items lying around (after picking up a multihead USB charging cable):
Nintendo DSi: works. No mods needed, just the proper power cable. Battery 3.7v 840 mAh 3.1Wh.
Sony Reader PRS-600: does not work. Have not tried with the short across the data pins. It registers as being attached to USB, but does not charge.
Samsung SCH-R500 phone (yes, its an old one): works. Just need Samsung charging adapter.
Blackberry Curve 8530: works. Battery 1150 mAh.
Garmin GPSMap 76CSx: cannot charge batteries through USB port, but does act as an external power supply.
That's all I have for now.