I second the travelling option, WWOOF (linked by EmeraldGrue above) in particular is great. There are tons of other volunteer opportunities if you look for them.
Most importantly, though: avoid hostels and backpackers. It is tempting to hang out with other Westerners, but you really miss out on most of what you’re travelling for. A hostel in Barcelona filled with Australians and Israelis is not too different from a hostel in Rio filled with Australians and Israelis, and overall it’s much cheaper to party at a hostel in Toronto with Australians and Israelis.
Other than that: volunteer at home. This will help you figure out what you like, what you don’t like, what you’re good at, and where you are needed.
Just remember, that on average the “life long career” doesn’t exist anymore (I recall from somewhere that the average American changes career – not jobs – 4 times) So don’t get hung up on what you’re going to do forever and ever.
Just do whatever. Pay your bills. Don’t have debt. Life below your means. Save money. Invest wisely. Then you’ll always be free to do as you like, and you’ll never be a slave to your paycheck.
Library work comes to mind; you spend a lot of time helping people (maybe more than you really want), you can work with kids (again, maybe more than you really want), and when you have a bit of downtime, there are books. The big downside is the job market (up and down, usually dicey) and going to graduate school, as you need a master’s degree for almost any library jobs more advanced than reshelving the books. Try volunteering at a local library, chat up the staff and see if it looks interesting and feasible.
Technical writer? That’s what I do. I read a lot, write a lot, and help other people a lot. Get to work in stuff like computers, biotech, etc. without needing a technical degree.