Invision - Prototyping and collaboration for design teams
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
Visualtip - A service that allows designers and clients to annotate and collaborate on images in real time
Sketch - Professional digital design for Mac.
Pastel - Sticky note-based feedback collection tool for live websites
Savahapp - The all-in-one design sharing, collaboration, workflow and app prototyping platform