NiMH cells are gaining wide popularity in, amongst other places, digital cameras. The energy density in NiMH cells may be lower than that of lithium ion cells, but the fact that they are, in most equipment, interchangeable with disposable dry cells makes them very attractive power sources. The similar electrical and mechanical considerations of NiMH and to dry cells, translates into a wide supply of relatively low cost cells. Also, in case of an emergency, you can always revert back to dry cells if all your NiMH cells are discharged. NiMH should under ideal charging conditions charge for 14 hours at 10% of their rated hourly capacity.
A CPU based NiMH charger - [Link]