iExit. Great app to know what is available at each exit on the interstates. Shows you several exits ahead and lists actual brand names (not just "gas" or "food") as well as how far off the highway they are.
Its smart enough to know what direction you are driving and only shows the exits ahead of you. Two versions, free and paid. We used the free version on a drive from MA to WDW in October last year and were so impressed with it we bought the paid version just to support the developer.