If you like drawing quietly in a sketchbook that’ll never see daylight, this app may not be for you. If you and your friends like trading sketches, though, Doodle.ly might be helpful: It’s a drawing app that puts a real emphasis on sharing. Users can trade and share sketches using Facebook, Twitter, Tumblr, iMessage, email, and AirDrop. iPad users can store up to 180 sketches at one time. And you’ll have a variety of drawing tools, ranging from crayons to fine-point marker and beyond.