In case if you are still monitoring this thread: I just got a Virgin prepaid Kyocera phone from BestBuy for $60 (after a $20 instant rebate). It comes with $10 worth of airtime (40 to 85 minutes based on how you use it). AND you instantly get a $15 BB Gift Card that you can use to buy more airtime or anything else.
Virgin does seem to be the cheapest as far as minutes go. They also allow you to keep them the longest: 90 days.