http://www.e85refueling.com/ If there is an E85 station near you, you can find it using that website. Around here, E85 is steadily around 40 cents per gallon cheaper than 87.
You could make some wicked cheap high octane fuel mixing in some E85. As I said earlier, 20-30% is no problem at all. If you mix 87 octane with 30% E85, you get around 93 octane. Starting with 93 gasoline should give you 97 octane.
For those with a blower, the 97 will allow higher boost. How much fun would an extra 3lbs of boost be?
For those stuck running premium, how would you like to make 93 octane for LESS than the price of 87?
As I said, 30% and less is perfectly safe and the computer will compensate perfectly. I've run 30% before and even put my wideband on to see the actual air fuel ratios. They are exactly the same and crappy as when I'm running streight 87 octane (13.5:1 in the mid range, dipping to 12:1 by 5000rpm)