Airbnb: The company that spurred the sharing trend with air mattresses in a San Francisco apartment. Lodging runs the gamut: an Amsterdam houseboat, a pullout sofa in Paris, an English castle. Accommodations are available in 34,000 cities in 192 countries. www.airbnb.com.
Tripping: The site has two personalities: vacation rental aggregator and playdate maker. As an aggregator, it searches for more than 850,000 rentals in 36,000 cities. As a social butterfly, the company fosters a community of travelers in 175 countries who play ambassador to visitors to their hometown. In addition to meeting for coffee or a more ambitious outing, many Tripping members also provide free home-stays. www.tripping.com.
Feastly: Professional and amateur cooks prepare themed or personalized meals in their home (or sometimes a public venue). You must sign up and wait for invitations to appear in your e-mail inbox. eatfeastly.com.
Meal Sharing: Helps travelers hunt down a home-cooked meal in 350 cities and 50 countries. www.mealsharing.com.
HomeDine: Find a dinner party in your destination and ping the host to request a chair at his or her table. Lists many free events, such as potlucks and housewarmings. homedine.com.
Shareyourmeal: The alternative to takeout: Pick up a meal prepared in a home kitchen in cities around the world. Be a good customer and bring your own container. www.shareyourmeal.co.uk.
RelayRides: Borrow Mark's Jeep Wrangler in Houston or Ryan's Subaru Legacy in Portland, Ore. Rent by the hour, day, week or month. Travelers deal directly with the owner, who sets the price. Airport pickup/drop-off available in many cities. relayrides.com.
Getaround: Rent someone else's ride when visiting San Francisco and the surrounding Bay Area; Portland, Ore.; Austin; Chicago or San Diego. Instant rental available on some cars, so you can just swipe and go. www.getaround.com.
FlightCar: Rent a local's car parked at Boston Logan or the San Francisco airport. Cars are listed in familiar categories, such as compact, coupe, sedan, SUV and luxury. GPS devices and car seats available for free. flightcar.com.
Lyft: If your real friend won't give you a ride, contact a Lyft pal, who arrives in a pink-mustachioed car and won't complain about how he could be doing something better than driving you around. Pay by donation, although the company suggests a fee. Offered in San Francisco, Los Angeles, Seattle and Chicago. Works by app only. www.lyft.me.
Boatbound: The newly launched site lists boat rentals by owners. Pickings include vessels powered by motor, sail or paddle. Owners may require proof of captaining experience. boatbound.co/search.
Spinlister: Grab a two-wheeler from individuals and bike shops in more than 40 countries. All types of bikes available. www.spinlister.com.
Vayable: Locals with certain expertise or interests lead tours in their home cities. Outings are often insiderish and niche, such as a hammam tour of Istanbul and a currywurst expedition in Berlin. www.vayable.com.