A Free Gesture Icon System – Cue
Desktop users are experienced enough to know how they can interact with a website, use shortcuts and get the most out of the browser.
For touch-enabled interfaces, things are different. There is a new question: "which gestures are supported by the app/website?".
Cue is a free (public domain) gestural icon system that aims to build a standard visual language of touch-based interactions.
There are icons for actions like swipe, drap, touch, tap and hold, spread and more.
Each icon comes in a labeled and unlabeled version and the set is in .PNG, .SVG Omnigraffle Stencil and InDesign formats.