Ocean Technology via Amazon offers Prime members the Unitek Detachable 4-Port USB Charging Station Dock, model no. Y-2187A, for $29.99. Coupon code "OG6XGKN6" drops it to $16.79. Plus, Prime members bag free shipping. (Non-members can spend $49 or more to qualify for free shipping; otherwise, shipping costs $7.15.) That's $3 under our mention from last November and the lowest price we've seen. (It's also the best today by $3.) It charges up to four devices at once, and is compatible with iOS or Android devices.