I haven't seen this posted here yet, and since so many of y'all use Mobil 1, I thought I'd post that I saw on Mobil 1's website
http://www.mobil1.com/ that if you send in proofs of purchase you can get rewards, which you can turn either into Mobil merchandise or a gift certificate. You gotta register on there first.
Not too bad a deal; I could always use another polo shirt, especially when I'm going to spend the money on the oil in the first place....
Steven