MockFlow provides a one-stop solution for brainstorming user interfaces that includes UI design mockups, sitemaps, documentation and design approvals.

Everypixel finds the best photos to help creative people save time, money and nerves.It is a powerful search engine that indexes 50 paid and free stock image websites, and allows users to search through a massive database of stock photos in seconds.

Giphy, styled as GIPHY, is an American online database and search engine that allows users to search for and share short looping videos with no sound, that resemble animated GIF files.

Free and premium mockups, UI/UX tools, scene creators for busy designers

Bulma is a free, open source CSS framework based on Flexbox and built with Sass. It's 100% responsive, fully modular, and available for free.