At AT&T, sign up for a select AT&T U-verse Broadband / TV / phone package and receive up to $250 in AT&T Reward Prepaid Cards for free. (Reward amounts start at $100 and a "U-family" U-Verse TV package or greater is required to begin receiving rewards.) That's tied with our February mention and it's the best reward card offer we've seen from AT&T in almost three years. (Reward Card offers typically top out at $200. Be sure to select "AT&T Promotion Cards" from the drop down menu when choosing your services.) Click here for complete details on reward requirements.
Note: Although plans start at $19/month (for TV only), the cheapest eligible for a prepaid card appears to be the U-Family TV service for around $29/month. It includes up to 130 TV channels and one DVR. (Plan prices vary by location.)