Whimsical Wireframes - Lightning fast wireframing with real-time collaboration.
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.
Balsamiq Cloud - Fast, approachable, collaborative wireframing
Invision - Prototyping and collaboration for design teams
Justinmind - Define awesome experiences through wireframes & prototypes.
Zeplin - Collaboration app for UI designers & frontend developers