Frequent-flier miles are great for other free vacation travel options, including free lodging. While you're typically restricted to major chains, they can be used for thousands of hotels nationally and internationally.

But that's not the only way to get a free place to stay. Websites such as HomeExchange.com are safe ways for you to trade living spaces with someone. If you have an apartment in New York and want to exchange it for one in Paris for a week in the spring, that's no problem. Looking for a beachside condo in exchange for your home next to the Rockies? That's a possibility, too.

Even better, you could get free travel perks that not even the best hotels can match, says Keghan Hurst, spokeswoman for HomeExchange.com. "A lot of our members will include access to their vehicles, bicycles and even boats," she says. "Everything is negotiable."

If you're not interested in exchanging spaces, CouchSurfing.net helps people find a place to crash for free, with nothing required in return but good manners.