[harpastum]

In the past I've had success using Parametrek to find good deals (and then doing my homework on the seller to make sure they're legit): http://batteries.parametrek.com/index.html?size=18650

Right now you can authentic 18650 Samsung cells for around $260/kWh, or 21700 Samsung cells for $165/kWh. Those are sale prices, but if you're careful and watch for deals, you can find them.