from http://www.dtv.gov, the official government site for the transition:
After February 17, 2009, full-power television stations will broadcast in digital only.
There is currently no deadline for (low power, Class A, and tv translator) stations to convert to digital broadcasting.
Every U.S. household is eligible to receive up to two coupons, worth $40 each, toward the purchase of eligible digital-to-analog converter boxes.
For more information on the Digital-to-Analog Converter Box Coupon Program, visit the NTIA’s website at www.ntia.doc.gov/dtvcoupon, or call 1-888-388-2009