Bit.ai - Bit is a smart real-time document collaboration platform for teams to create interactive documents, manage digital content and track document insights.
Zeplin - Collaboration app for UI designers & frontend developers
Google Docs - Create a new document and edit with others at the same time -- from your computer, phone or tablet. Get stuff done with or without an internet connection. Use Docs to edit Word files. Free from Google.
Mightytext - Send & Receive SMS Text Messages from your computer. Sync'd with your Android #
Airborn - Create and edit documents online without sacrificing your privacy
Abstract - A secure, version-controlled hub for your design files