Edshelf is a constantly-updated directory of apps and extensions that is organized by grade level, academic subject, or task (presentations, flashcards, augmented reality, etc.). You’ll get reviews of the apps from educators (which is why I likened it to Yelp!) – and the reviews contain useful information, like whether you need to pay money to use apps, or how easy/hard the learning curve is. There are also “shelves” where people curate their lists of apps, so if you find a like-minded teacher, you can follow him. It’s very user friendly – check it out!