Free plane tickets
For air travelers, the currency of choice for free vacation travel is the frequent-flier mile. There are an almost infinite number of ways to get to 25,000 miles, the base requirement for domestic trips.
One option: Grab any of the numerous credit cards that offer a sign-up bonus of at least 25,000 miles, says Chris Guillebeau, founder of Travelhacking.org.
"Credit cards are definitely helpful for earning big bonuses all at once," he says, noting that some sign-up bonuses offer a generous 50,000 miles or more.
You can also snare miles through hotel stays, credit card purchases and purchases through airline-branded shopping portals, like American Airlines' AAdvantage eShopping Mall and Delta's SkyMiles Shopping.
To make the most of your miles, remember to time your reservation wisely. "Reserve at least 90 days in advance or less than 14 days before departure to get the best odds" of booking a ticket, Guillebeau says. If you don't get what you want online, call the airline with requests for different flight options, hub cities and partner airlines to get the flight you want without burning through your miles.