Very recently, Facebook launched its new "Marketplace" classifieds ads feature, a potential rival to services like Craigslist. The service, according to a New York Timesarticle, was supposed to go live on Friday. At least in the networks that I have access to, it wasn't actually available until Sunday night. (Facebook occasionally will roll out features to select school, workplace, or regional "networks" within the service before they become widely available. But it looks like now the Marketplace is available to everyone.)
Look for our review of Facebook Marketplace very soon.