Abstract - A secure, version-controlled hub for your design files
StatusOk (Open source) - Get notified through Slack/email when your website is down
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
Owlead - Grow your Twitter with valuable followers, effortless
Sketch for Teams - Take design collaboration to the next level in the cloud
Adobe XD - Adobe XD is an all-in-one UX/UI solution for designing websites, mobile apps and more.