http://www.gasbuddy.com/
I copied the URL and pasted it. Is that what you mean Al?
I have used this often, and find generally speaking diesel prices away from the interstates are much less. The downside is some of the fuel stations are not bus friendly. I use this in concert with Google where I will zoom in on a satellite view to see if it looks like I will have room to get in.
One thing I learned the hard way is if I am really low on fuel and I am trying to fill at some of the small local stations that the small hose used for diesel pickup trucks takes forever to fill 200 or more gallons, and in some cases they will not sell more than $75 or $100 worth at a time.