From Literature and Latte:
Scapple is an easy-to-use tool for getting ideas down as quickly as possible and making connections between them. It isn't exactly mind-mapping software--it's more like a freeform text editor that allows you to make notes anywhere on the page and to connect them using straight dotted lines or arrows. If you've ever scribbled down ideas all over a piece of paper and drawn lines between related thoughts, then you already know what Scapple does. Scapple doesn't force you to make connections, and it doesn't expect you to start out with one central idea off of which everything else is branched. There's no built-in hierarchy at all, in fact--in Scapple, every note is equal, so you can connect them however you like. The idea behind Scapple is simple: when you are roughing out ideas, you need complete freedom to experiment with how those ideas best fit together. Creating notes is as easy as double-clicking anywhere on the canvas and then typing; making connections between ideas is as painless as dragging and dropping one note onto another. And unlike with paper, you can move notes around and never run out of space.