2009, The Washington Post Planning to incorporate biking into an upcoming vacation? There are more options than ever, with the popularity of folding bicycles, urban bike-sharing programs and the possibility of reserving a rental bike online. Here are a few options and Web sites for the two-wheeling traveler: Folding bikes With most airlines now charging more than ever for checked baggage, checking bicycles that exceed airlines' size and weight limits (usually 62 linear inches and 50 pounds) can add up, costing from $50 on Southwest to $300 on Delta's international flights. Having a bike that fits into a suitcase and can be checked as standard luggage can make a lot of sense -- and save a lot of money. George Farnsworth, webmaster of Bike Access (www.bikeaccess.net), takes a yearly bicycle touring trip and says he uses the foldable Bike Friday when he flies. 'The gearing is adjusted so that the wheel size doesn't matter,' he says, though he notes that the smaller 16-inch wheels 'make bumps feel bigger, and maybe the steering's a little quicker. You can't even think about riding no-hands.' However, he notes that folders are similar to standard bikes and can handle the weight of panniers for toting gear for long trips. Several companies, including Montague and Dahon, make folders with full-size wheels. Folding bikes can be more expensive than their standard counterparts, with the $300 tiny-wheeled A-bike (www.a-bike.co.uk) among the cheaper options. Still, for folding bikes' main users -- commuters -- having the option to take a bike on a flight can make the investment worthwhile. For more information, visit the Folding Society's Web site, www.foldsoc.co.uk. Bike-Sharing Throughout Europe, hundreds of cities and towns have established bike-sharing programs, many with day memberships for visitors. Here's how most programs work: Members unlock bikes at designated racks by swiping electronic cards or prepaying with credit cards at attached kiosks, ride the bikes, then return them to other racks. Some programs charge an annual fee and allow unlimited rides; others charge per ride. Washington and Montreal are the only cities in North America with public bike-sharing programs; other cities in the United States and Canada have plans. Paul DeMaio, founder of MetroBike, created and maintains a blog with an interactive map of bike-sharing cities across the globe, bike-sharing.blogspot.com. He points to Paris's Velib program as a turning point in the popularity of bike-sharing. When Paris launched Velib in July 2007, it had about 10,000 bikes in its fleet, dwarfing any similar program at the time. 'Most programs are designed to be tourist-friendly,' DeMaio says, but since they're generally designed for short trips rather than sightseeing, programs have time limits on bike use, like three hours for Washington's SmartBike, or start charging after the first half-hour, like Velib. In places like Copenhagen, whose system uses older technology, it's possible to keep the bike longer, but usually, DeMaio says, 'for touring, bike rental shops are the best option.' Rentals Early this year, www.rentabikenow.com popped up, allowing users to rent bikes from independent shops across the United States and Canada. You can see the make and specifications of the bikes available and book in advance, paying a portion of the rental cost as a deposit. Some national chains, such as Bike and Roll (www.bikeandroll.com), which has branches in Chicago, Miami, New York, San Francisco and Washington, also offer online bookings. Tips If your destination is in the United States or Canada and you plan to take public transportation, find out what the rules are regarding bikes on transit systems with the Bikes on Transit database (www.bikemap.com/bikesontransit/index.php). 