Photo by Jim G
Graham Hughes has traveled the entire world, on a shoestring budget, without using a plane. It took him almost four years to do so and he spent about $100 per week. When I say "the entire world" I mean "every country on the planet". I have friends who have traveled all over South America and Europe on just a handful of money. In fact, if you really have courage, dumpster diving can keep you fed in many of the wealthier nations.
Or you can read about Benny Lewis of Fluent in Three Months, another traveller who explains how to travel the world on a shoestring budget.
The Guardian has a short article on how to travel the world on a budget. The Matador Network carries a similar article. Verge Magazine has yet another. Heck, hit your favorite search engine and look for travel the world for free and you're going to be inundated with different strategies. There's an embarrassment of choice. It's the difference between wishing you could see the world and getting off that chair and doing it. What's stopping you?