By now, we all know what social networks are. Chances are you're signed up for at least a few, like Facebook, Instagram, or LinkedIn. Besides the most popular social sites, there are thousands of smaller niche sites that might give you a more personalized experience, catering to your real interests. Travelers will love city guides on Foursquare, and Nextdoor gives neighbors a platform to connect on virtually. Here you can look for new sites to join or for reviews about the one you already have in mind.