Chameleon Design System

Chameleon contains symbols and templates for both desktop and mobile applications (340 basic symbols and components with 60+ web and mobile templates) for you to adjust and use in your projects. It was created with Atomic Design Principles as a base line, with up-to-date industry best practices (4x and 8x dp grid for best possible scaling, 12 column layout for responsiveness, icon bounding boxes and more). With Chameleon you can create a lot of different products – it is suited for big multi-platform, multi-system apps as well as simple web pages.

You can download it for free at UI8: https://ui8.net/gui-kit-point/products/chameleon-design-system-for-sketch

Edit 2023: This project is discontinued, but you still should be able to download it at UI8.