StartupResources.io - Tightly curated lists of the best startup tools
Flowkit - Sketch library for user flows/content maps/annotations
Startup Stash - A curated directory of 400 resources & tools for startups
Crystal: Sketch Mirror for Android - Crystal: Sketch Mirror for Android is an application that is designed for viewing your sketch designs in real-time, navigate prototypes and download content related to the sketches for offline viewing.
Happy Startup Canvas - A simple framework for building stuff that matters
Figma Mirror - Figma Mirror is an application that covers top trending designing or sketching ideas making your teamwork in a single environment and design better products from start to finish.