Splitwise - Splitwise is a free tool for friends and roommates to track bills and other shared expenses, so that everyone gets paid back. On the web, iPhone, and Android!

Figma - Team-based interface design, Figma lets you collaborate on designs in real time.

Dinngo - Splitting payments the fun and easy way

InVision Studio - The world’s most powerful screen design tool

/Tab - The simple way to split a bill among friends.

Design Principles - An open source repository of design principles and methods