Device Shots - Generate high-resolution device mockups using a screenshot.
POP (Prototyping on Paper) - POP helps you make interactive prototype with ease. If you can draw, you can design apps.
shotsnapp - Create beautiful device mockup presentation
Marvel - Turn sketches, mockups and designs into web, iPhone, iOS, Android and Apple Watch app prototypes.
Base UI Sketch Framework - Huge set of everything you need to design and prototype
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.