Jumping off of the previous discussion about Hotel Loyalty programs, I thought it would be worth taking a look at the programs offered by the various gas station chains across the country.
This summer, BP has a great deal through their Driver Rewards Program, where you earn 25 cents off per gallon for every $100 you spend. Your discount is earned with each fill up, so if you spend $50 to fill your tank, you've earn 12 cents off, which you can use at your next fill up, or keep building your rewards and get a big discount all at once. The discount is good for up to 20 gallons, but can only be used once, so you get the best deal if you wait until your tank is on fumes to fill up!
I see that Exxon/Mobil also just launched a new rewards program called Plenti, where you can earn credits at their stations, as well as a variety of other stores, but I haven't looked into it much yet.
Shell has its Fuel Rewards program, where you automatically get 3 cent off every fill up, plus you can earn larger discounts by making purchases inside Shell stores and other locations.
There are also lots of other regional chains that offer discounts on gas, usually 3 to 5 cents a gallon, if you use a loyalty card. Speedway (Midwest), Super America (Minnesota), Sheetz (Mid-Atlantic) are a few of the ones I have in my collection. Of course, most of the big grocery store chains - especially Kroger (which goes by many different names, depending upon the state) - also have cards that will give you a discount at their gas stations, and are also used to get discounts on groceries.
Of course, the thing with loyalty programs is that you have to make sure you're still getting the best deal. If you go to a station to save 3 cents using their rewards program, but that station is charging 10 cents more than a station across the street, you're not saving anything!