Microsoft Office Visio, draw.io, Lucidchart, PlantUML, Google Drawings, yEd Graph Editor, MindMeister, Freeplane, Mind Mapping 3D, WireframeSketcher, LibreOffice - Draw, Flinto, Mockup Designer, Brainboard, DeepNotes, Plectica, GlooMaps, GraphUp, Zen Flowchart, Wireflow, Venny, MockupCreator, GeneVenn, Diagramiq, WriteMaps, Thinking Space, Syngraph.me, Holori are some alternatives to Cacoo.