Mockplus!

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.

Axure RP is the leading tool for rapidly creating wireframes, prototypes and specifications for applications and web sites.

UXPin is a web-based system for managing design documents like wireframes, sitemaps, persona descriptions or flowcharts. It lets you upload image files, invite teammates to review and comment on them, and keep track of revisions. The system also includes its own wireframe editor that supports real-time collaboration and allows you to export your wireframes to HTML. Another feature worth noting is that UXPin can convert paper prototypes into digital wireframes as long as they have been created using an official UXPin notepad (available for $30 on their website). You simply take a picture of the prototype and it will automatically be recognized by the UXPin app. Prices for UXPin start at $7 per month for a single-user project. »

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.

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.

Mockup Designer, built with Backbone, Backbone-LocalStorage and Html2Canvas, is a super-easy-to-use mockup tool that uses the local storage of your browser as its backend. However the data layer is loosely coupled, so you can integrate with any RESTful API or any Backend service.

"The most stunning HTML5 App for creating high fidelity, resolution independent SVG mockups and wireframes!"

A functional wireframe is the best way to reduce costs of your software projects. Simulate your wireframes and mitigate risks.

mockingbird is an online tool that makes it easy for you to create, link together, preview, and share mockups of your website or application.It is not Flash based.

Design your software or website mockups within minutes. Mockup Builder is a new look to solve old problem with prototyping and sharing sketches with customers. This startup was built to solve developer’s needs in product that can help to make it better communication tool between developers and clients in site developing process.

HotGloo is a UX, wireframe and prototyping tool designed to build wireframes for web, mobile and wearables. HotGloo helps to visualize planning processes, build and test drive interactions very easily. Create and share fully interactive prototypes with your team and clients and gather feedback on the process. From prototypes of the next award winning app to huge e-commerce wireframe shop solutions, HotGloo is the perfect match for every web worker.

UX-App V2 is out (December 2016), try the most flexible and extensive product planning experience in the market today! Register and get 1 evaluation project + 1 user invite free.

Quickly create, share and simulate professional wireframes, mock-ups and UI prototypes online without programming. Pidoco is an easy-to-use web-based prototyping application that comes with real-time collaboration and usability testing features and can speed up your projects by over 50%!

Upload your designs,mockups or wireframes by file or by URL snapshot, organize them and connect them to web prototypes. Share them with friends, colleagues and clients to get point specific Feedback. Giving Design Feedback is also possible without any registration.