draw.io - Online diagramming application
Roomtodo - Simple yet powerful online tool for interior design and floorplans with built in walkthrough module.
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.
InnoPlanner - InnoPlanner is a commercial based interior designing software.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
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.