Today only Black & Decker 20W Power Backup Battery Pack - 2 Pack@$10 + $5 shipping
Mostly for low wattage lights and electronics like a GPS. But cheap. and has both USB and a 110V outlet built in. You might be able to charge it off a hub. charger is 12V dc.
2000 Montague CX, I do not recommend it, but still ride it.
Strida 3, I recommend it for rides < 10mi wo steep hills.
2006 Rowbike 720 Sport, I recommend it as an exercise bike.
1996 Birdy, Recommend.
Wieleder CARiBIKE (folding), decent frame.