If you're looking only at synthetics, the best price deal right now might be getting two 5 qt bottles of Mobil 1 0w-30 for $22, then using the $10 rebate to bring them down to about $12 each.
Next, buy the Purolator PureOne filters from Amazon for $9.50 for two (make sure to add it to other items you're already buying to get the free shipping). Then using the Purolator rebate to get $2 back off each one.
Assuming you got free shipping at Amazon, that's two oil changes using Mobil 1 oil and Purolator PureOne filters for just under $15 each. Obviously that's excluding taxes on the oil and the cost of the stamps to send in the rebates, it also assumes you get your rebates, etc etc etc.
I'm not going to debate which oil or filter is best, but I think everyone will agree that Mobil 1 0w-30 and PureOne filters are both very good products.
Anyways, based purely on final price, I think that's the best deal that I know of right now