Sweet Home 3D - Sweet Home 3D is a free interior design application that helps to draw the plan of house, arrange furniture on it and visit the results in 3D.
draw.io - Online diagramming application
Planner 5D - Home Design Software & Interior Design Tool ONLINE for home & floor plans in 2D & 3D. Read more about Planner 5D.
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
SketchUp - 3D for Everyone
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.