Origami Studio!

Pencil is a standalone app or Firefox extension that lets you create diagrams or UI mockups. It doesn't have collaboration/multi-user features.

Using Balsamiq Mockups feels like you are drawing, but its digital, so you can tweak and rearrange controls easily, and the end result is much cleaner. Teams can come up with a design and iterate over it in real-time in the course of a meeting.

InVision's prototype tool lets you create interactive wireframes and high-fidelity prototypes. Share your work and get instant feedback right on-screen.

Framer combines the power of code with the ease of visual editing. Prototype beautiful microinteractions or realistic apps. It’s time to design with development in mind.

Free web and mobile mockup tool.Transform your design and mockups into clickable interactive applications. Perfect way to validate ideas faster with lean startup thinking.

"Go from idea to prototype faster with Experience Design CC (Beta), the first all-in-one cross-platform tool for designing and prototyping websites and mobile apps. Test-drive the beta and watch the video to see how we’re evolving XD to bring you exciting new ways to collaborate and deliver a whole new experience in user experience." - Adobe.com

Principle makes it easy to create animated and interactive user interface designs. Whether you're designing the flow of a multi-screen app, or new interactions and animations, Principle lets you create designs that look and feel amazing.

Flinto for Mac is a comprehensive app prototyping tool that allows you to create anything from simple tap-through prototypes, to comprehensive prototypes with impressive interactions. We’ve carefully designed Flinto for Mac to minimize complexity. There’s no programming or timelines. It’s the prototyping tool designers have been waiting for.

Prototype mobile interactions as easy as Pie.Compose elaborate interactions and animations easily, and build sensor-aided prototypes without a line of code.

Fluid UI is the fastest mobile app prototyping tool available. Design and test your low and high fidelity app mockups on a mobile device with ease. Simple and UX oriented, this UI tool helps unlock creativity and will save your team time and money while gathering app requirements.

Generate styleguides and resources automatically from a Sketch file, to facilitate the hand-off between design and development.

Nothing to download/install, create and access your mockups from anywhere.

Pixate generates 100% native prototypes, so you can experience your ideas on device as if they’re completely real.

Comp CC makes it easy for designers to lay out ideas with real assets like photos, text and shapes. They can then send the wireframe to Photoshop CC, Illustrator CC, InDesign CC or Muse CC to refine and finish.