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.
Roomtodo - Simple yet powerful online tool for interior design and floorplans with built in walkthrough module.
OmniGraffle - OmniGraffle is for creating precise graphics like website wireframes, an electrical system designs, or mapping out software class.
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
Palette CAD - Palette CAD is one of the easiest 3D design software for those people who want to use a simple to use program for interior designs.