Ultracaps:
From Maxwell - a breadbox containing 22 of 2600 Farad capacitors
The first ultracap they made used powdered carbon and a
"small-ion" electrolyte.
Other products: 2.7kF caps cost about $50
18 kJ per kg specific energy.
Discharge currents as high as 1000A at 2.5V
Fuel Cells:
From Toshiba, a prototype - 100mW
Runs up to 20 hours on 2cc of conc. methanol.
Tanked up weighs less than 10 gram