It's a common problem—your shiny new laptop isn't looking so shiny or new anymore, and what's that? The battery barely holds a charge now? Ugh. I'm skeptical of Leyden Energy's claims, but would give their batteries a shot.
They claim their lithium-ion, 440watt hours per liter batteries don't depreciate for at least three years (supposedly normal ones start losing their charge around the 18-month-mark), and as they come with a three-year warranty, that's something you can obviously take them to fault with if you discover it's all bullshit.
Able to operate in higher temperatures than normal batteries, they can also be charged over 1,000 times. While they'll cost a lot more than the usual laptop batteries (supposedly less than double the average cost), it might be a cost worth paying. They'll be available online in the coming weeks in Canada at Dr. Battery, and hopefully in other countries after that. [Leyden Energy via Gigaom]