While memes and bluster often overwhelm substantive debate, fact-checking has emerged as an important -- and growing -- counterforce. More than 100 fact-checking projects around the world actively hold politicians, public officials and other institutions accountable for what what they say and promise. Other projects debunk hoaxes and dubious claims that infect public debate, often through social media. Many fact-checking efforts are affiliated with media organizations or staffed by people with journalism backgrounds. But other models thrive, too -- including growing communities of non-profit organizations and citizen watchdogs. In this panel, representatives from four top fact-checking ventures will discuss trends, including the ways technology and social media extend their reporting and engage the public in finding and spreading factual information.