Adobe XD is a commercial vector user experience design tool for designing web apps and mobile apps

Balsamiq Mockups is a rapid wireframing tool that helps you Work Faster & Smarter.

Creately is a collaborative diagramming and design software used by teams around the world to communicate more effectively.

Diagram Designer is a vector graphics editor that allows you to create UML class diagrams, illustrations, flowcharts and slide shows.

Diagrammix is a tool for efficiently building attractive diagrams and flowcharts.

Edraw Max is comprehensive mind mapping and planning tool network diagrams, floor plans, workflow diagrams, business charts, and engineering diagrams.

Axure RP is a wireframing, rapid prototyping, documentation and specification software tool aimed at web and desktop applications.

ConceptDraw PRO is diagramming software used to create business graphics, including ConceptDraw Flowcharting Suite.

Dia is free and open source drawing software.

draw.io is free online diagram software for making flowcharts, process diagrams, etc

Diagramo is an online flowchart software. It's FREE and Open Source ( GPL ) It's pure HTML5 Share and collaborate.

Fluid UI is a browser-based wireframing and prototyping tool developed by Fluid Software and used to design mobile touch interfaces.