Hybrio batteries by Everlast are said to last four times longer than everyday alkaline batteries and can be recharged 500 times. The kicker here is the price, though, with a four pack including a charger costing around $28. If they can last as long as the company says, these suckers will pay for themselves after just a few charges. They'll be available in late October.
Product Page [Hybrio USA, via treehugger]