MapQuest Driving Directions: Type in your starting point and your destination, and MapQuest will give you a map and detailed driving directions. To print, click on the "Print" link to the left above the driving directions. This goes for the MapQuest Road Trip Planner and MapQuest Canada as well.
National Geographic's Map Machine will create detailed road maps for you. You can print these maps easily by clicking CTRL P on your computer keyboard (the CTRL key, then P).
Google Maps has printable driving directions; you'll see a Print icon to the far right of the directions page right above the map. Click on that icon, and you'll be able to print. Google Maps also offers printable walking directions.