•  If you want to make friends at hostels: Youth hostels are, in general, very social places, but the iPhone app WeHostels aims to make them even more so by enabling travelers to meet one another before they even check in. To use the app, select a city, enter your travel dates and then browse its top five hostels as well as the profiles of people who plan to stay there.

Bottom line: A particularly appealing idea for solo travelers hoping to meet fellow tourists, though you have to book a hostel through the site (which offers only five hostels in certain areas) in order to communicate with other people staying there.

•  If you want to hang out with the locals: Triptrotting.com connects travelers with locals for advice and activities like bike riding in Beijing or a photo tour of New York landmarks. And while it’s not a dating site, the algorithm it uses to match travelers — based on qualities like interests, personality and profession — was created by a former chief scientist at the dating site eHarmony.com.

Bottom line: Like other such sites, this is an easy way to find like-minded adventurers. But because it’s new, it has fewer members than more established sites like Couchsurfing.org.

On Globetrooper.com, users can post a trip they’re planning and invite strangers to join. People using the site can see the trip details. If they’re interested in participating, they “follow” the trip by clicking a button, which in turn enables them to post comments and ask questions about it to see whether it is indeed something they want to do. If they decide that it is, they confirm their participation and agree on a starting point.

Bottom line: This site may help you find some wonderful people, but as with all sites like this, be cautious and get as much information as possible about your potential travel mates before agreeing to meet. Also, this site is for more adventurous travelers. Among the trip categories: “altitude 4000m+,” “motorcycle touring” and “overland & safari.”

•  If you want to meet a friend of a friend on a plane, in a museum or at a bar: Banjo, an app for iPhone, uses location technology to facilitate spontaneous meetups while you’re on the go. Its creator, Damien Patton, came up with the idea after learning that while in an airport he missed connecting with a friend he hadn’t seen in years. Both of them had posted their locations on social networks — but not the same ones. Banjo is designed to ensure that sort of thing doesn’t happen; it combines all your social networks into a single stream of real-time updates.

Bottom line: Streamlining social media is always helpful, but to use this app you must have a Twitter, Facebook, Foursquare or Instagram account and allow the app to have access to it.

Another location-sharing technology app, Highlight, is for iPhones and Androids (it requires a Facebook account to log in). The app notifies you if your friends are nearby. Additionally, if people in your vicinity also have the app, their profile appears on your phone, along with their name, photos and any mutual friends.

Bottom line: This futuristic social tool is a hit with technology wonks and social butterflies. If you would rather retain your anonymity when at the mall or the park, take a pass.

Planely.com matches you with fellow airline passengers, allowing you to connect with them on the Web before you connect in the air. How to begin? Log on to Planely and enter when and where you’re going. The site then uses its members’ Facebook and LinkedIn accounts to not only show you other travelers you might know on your flight, but also things you might have in common so that you can chat with a wine enthusiast, share a cab with someone staying at your hotel or discuss the conference you’re both attending at the crack of dawn.

Bottom line: Planely is made for those who like to network or schmooze at 30,000 feet. If you would rather be taking a nap, it’s plainly not for you.