Camping
Camping is a great way to reduce costs, especially when camping wild, that is not in a paid for spot.
Legality
Wild camping is legal in Norway, Sweden, Finland, Scotland. add more
It's not very legal in Western Europe but you can usually get away with it if you camp in a hidden spot and/or leave early morning the next day.
United States
boondocking.org offers a web application which will allow you to enter GPS coordinates for your favorite camping spots, and find spots near your current location. Combining a mapping program and a GPS, now you should always be able to find free camping on your favorite public or private lands.