If air travel is your method of choice, there's no cheaper way than airlines like Southwest Airlines or Ryanair.  Low-cost carriers are used more frequently and are relatively inexpensive -- unless you've got to reschedule that flight, need to carry more luggage, or violate any of a host of fees that add to the ticket's cost.

The Economist, via Amadues, has released a map detailing the range of countries that rely most heavily on low-cost airline services.  Countries that are more red have a higher percentage of citizens that rely on the cheaper alternatives to flying.

The Philippines were the nation with the largest percentage of citizens using budget airlines at 65% of all passengers using these services.  Russia, Japan, and China all had markedly low use, at 5%, 4%, and 1% of passengers using budget carriers, with China's fierce protection of the nation's three major airlines being cited as reasons for low participation.