Moqups is a free all-in-one web app that facilitates collaboration on diagrams, mockups, wireframes and design prototypes. All work can be kept in sync and users can switch seamlessly between tasks. Extra pages can be added to link ideas. The range of stencils is flexible and adaptable while you can also upload your own images. Fully customisable settings allow full-scale collaboration or read-only sharing. Moqups is comprehensive and exceptionally fast. The free plan offers 300 stencils and 5MB storage. Further upgrades are free for education or non-profit companies.