Museums are a favorite attraction for many visitors, but getting in can cost an arm and a leg. For example, New York's Museum of Modern Art carries a hefty $20 price tag. But nearly every museum has a pay-as-you-wish or free time period each week or month, when you're not required to pay a dime. You can find these times and dates for eight major cities here, or type in "free museum day" and the place you're considering into a search engine.

If you're looking for free vacation travel perks at a national park, you also can get a break there. While more than 100 national parks charge entrance fees, they go fee-free on 29 days each year. You can see if any of the dates coincide with your vacation on this government website.

Finally, keep in mind that sometimes you don't need to pay to get a fantastic view of the city, Dudar says. "The Staten Island Ferry in New York and the Algiers Ferry in New Orleans are both free," he says. "They're both remarkable ways to view the skyline from the water. When it's a warm, summer day and you're getting a breeze on the water, it's a great way to beat the heat."