27. Free is the magic word. Check Traveler's Free Cities Index to discover freebies at your destination. Madrid's Museo del Prado, for example, offers free admission on Sundays. In London, the National Gallery, the British Museum, the Tate Modern, and the Museum of Natural History are all free, as are the Smithsonian museums in Washington, D.C. Plan ahead to maximize your chances of visiting an attraction when it's free, and keep a notebook with a listing of free activities in the city; this way you won't fall into the trap of spending money to kill time. Next time you have time to spare, you can pull out your book and find a free site nearby.

28. Buy theater tickets the day of the performance. Booths in London and San Francisco, for example, sell tickets the day before the show for a fraction of the cost. At the two TKTS kiosks in Manhattan, discounts range from 25 to 50 percent when you purchase tickets the morning of the show. Other great ways to find discounts of up to 50 percent on Broadway shows: Theater Mania, Playbill, and Broadway Box. For off-Broadway productions, check out Off Broadway Online.

29. Invest in CityPass. These little booklets offer admission to dozens of attractions—plus discounts at local restaurants and shops—for one low price. You can buy them for several U.S. cities in addition to Toronto, Canada.

30. Purchase a multi-day subway pass. If you plan to make several stops, you'll save a bundle. Pick up a brochure at the information desk or kiosk in the local metro or subway station for more information. For details on subways in New York, Boston, and Washington, D.C., log on to HopStop.com.

31. Book your adventures after arriving in your vacation spot—often local tour operators will offer better rates, and supporting the local economy is always a good thing.

32. For domestic travel, buy an $80 Annual Pass that covers the entry fee to thousands of federally managed recreation sites, including National Parks.