Maps are essential to hitchhiking. Make sure you always have a good map with you, the scale should at least be 1:700.000. In Western Europe and a few other countries it is very important to have a map that shows petrol stations, service areas, toll gates and other important places on the motorways.
You want to know were you are going. It also helps if petrol stations are marked, and you don't need city maps. Try and find a map that you don't have to open out to one large sheet of paper every time you want to use it; you will be using it often. Book-style maps are best.
AKAIK you've got the asnwer in one!
You can use Hitchwiki Maps, which is designed for Hitchhikers and includes eg. Hitchhiking places.
On most modern mobile phones, there are mapping applications. For Java enabled phones (almost any phone), you can use MGMaps, which uses maps from Google, Yahoo, Microsoft and even OpenStreetMap. It also supports GPS, if you have a receiver built-in or via bluetooth.
The Nokia N810 runs GNU/Linux, its GPS function is not great but it works okay in cars. You can easily get a lot of maps for the proprietary built-in software, at least for Europe, North America and some other parts of the world. Maemo Mapper is free software with loads of options, by default it downloads the maps from OpenStreetMap but you can also change it to use Yahoo or Google Maps.
- Check High-tech hitchhiking for some more information about using your mobile phone and other devices on the road