According to a tweet by @windowsphone, if you've purchased a Windows Phone from AT&T within the past thirty days, you may qualify for their "Buy One Get One" free offer.  The offer includes the Samsung Focus, LG Quantum, and HTC Surround.

Remember, the offer requires a two-year service agreement and a minimum $15 data plan per phone. Just check with your local AT&T Retailer to see if your purchase qualifies for the offer.