Amazon is wrapping up a huge sale on Droid phones this weekend, a sale that's tagged four different smartphones the cost of a mere penny. That's right. Those interested can pick up the Motorola Droid X, HTC Droid Incredible, Motorola Droid II, or Motorola Droid Pro for a mere $0.01.

So what's the catch?

As expected, Verizon is sponsoring the offer—as well as an activation fee credit for up to $35. However, to benefit from the penny sale, you must be a new Verizon customer agreeing to the customary two-year service agreement. Nevertheless, it's a pretty phenomenal deal for those looking to jump ship, given that the Droid Incredible itself retails for $600 on Amazon. Potential purchasers have until Monday to pick up a heavily discounted Droid device.

Three out of the four phones—the Droid II, excluded—are currently backordered at Amazon, likely as a result of the sale. Even though Verizon might appear to be losing money on the basically subsidized phones, customers will still have to choose from one of the company's six service plans for voice and texting, as well as one of two different plans for actual data service. The cheapest plan for voice and text messaging starts at $59.99 per month, and an unlimited data plan starts at $29.99 per month.

However, it's not as if Amazon's Wireless store is only constrained to four Android phones for its big penny sale. Approximately 34 other smartphones from various manufacturers (and supporting various carriers) are also being offered for the low price of a single coin, including offerings from Samsung, RIM, and—oddly—the Microsoft Kin One.

It remains to be seen just how much fire-sales of Android phones will help boost adoption rates for the platform versus its chief rival, Apple and its iPhones. As we reported yesterday, a September survey of approximately 4,000 people indicated that 37 percent would prefer to purchase an Android-based phone versus 38 percent that would prefer an iPhone.