Here are some of some useful websites and ways of traveling for less or even free!

As we all know, Hitchhiking is free. It is when people heading in the same direction as you take you as a favor.
Hitchwiki is a portal that shares information about the specifics of hitchhiking in particular countries, on how to travel hitchhiking.

BlaBlaCar and Liftshare are both websites where people can share rides to reduce costs.
This is very popular in Europe.

For flights, I recommend SkyScanner or Kayak as they let you compare many different fares and let you see
the fares for specific days in the flexible dates or calendar view.

For buses, I’ve been told BlaBlaBus which operates mostly in Europe has the best deals.