Ocean Technology via Amazon offers Prime members the Unitek Detachable 4-Port USB Charging Station Dock, model no. Y-2187B, for $34.99. Coupon code "8G73MQEJ" drops it to $22.04. Plus, Prime members bag free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $7.47.) That's $48 off list and the lowest total price we could find. It charges up to four devices at once, and is compatible with iOS or Android devices.