1. Don't pack extra stuff. Every 100 pounds of gear can reduce fuel efficiency by 1-2%. That adds up.
2. Do pack a cooler with food. Plan your meals on the road to be picnic-style and pack sandwiches, fruit, pre-cut veggies, and yogurt. Drink water. (Or drink coffee as needed.)
3. Bring along a travel coffee mug. Most coffee shops give a $0.10 discount if you have your own mug. That can add up depending on your coffee requirements!
4. Check gasbuddy.com for gas deals along the way.
5. Consider camping out at a public campground along the way instead of staying in a hotel.
6. If you do go to a hotel, find out if they offer free breakfast.
7. Rent books on tape from your local library.
8. No GPS? Borrow one from a friend.