Geocaching
Since many people have cell phones with advanced applications, you can hide an object in a park, at a bus stop or in a shopping mall. Give only the longitude and latitude coordinates for the clue and watch the teams use the GPS apps on their phones to try to be first to reach the object. Find the coordinates of the spot by using a GPS yourself, using Google Maps or following the tutorial at GPS4touring.com. This activity is also known as geocaching and if you don't want to hide an item yourself, you can find a geocache someone else has hidden and use it for your Amazing Race destination.
Check Out the Library
Give the teams a clue that is a quote from an old, obscure book in your local library. Ask the librarians to help you choose an old book or quote and let them know that you will have some (very well-behaved) people coming into the library searching for the book. Place the next clue inside the volume on the library shelf for the teams to find when they discover which book to look in. Be very clear with the librarians about what you will be doing, so you will not surprise or offend them; they will likely be very willing to help out if you approach them ahead of time.
Photo Finish
Take photos of several things around your town and give the contestants instructions to find the items in the photos and take their own pictures in front of them. For instance, take pictures of a statue or piece of art in town square, a photo of half of the sign on a storefront, an interesting mailbox or fire hydrant. Choose things that your contestants have either seen before or could figure out where they are located within the time limits of your game, but don't make the photos too easy to identify.
Game Details
Have bonus prizes for the first teams finished at each leg. An extra hint for the next leg of the race, or a $5 gift card for coffee or music downloads. Use creative methods for giving clues; embed clues in silly poems, use crossword puzzles, riddles or Morse code to make the race more exciting.