http://www.codinghorror.com/blog/archives/001078.html

In general you want the "hybrid" or "pre-charged" varieties, and should ignore ridiculous claims about capacity.

Most bundled battery chargers are junk. Given the inherent compromises of charging, you need something smart. That's why I ended up tossing my generic "rapid" chargers in favor of the majestic, glorious, and surprisingly inexpensive La Crosse Technology BC-900 AlphaPower battery charger.