yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.
VirtuallyShow.com - VirtuallyShow.com is an online affordable and feature-packed virtual tour service that allows you to create your residential and commercial real estate virtual tours in just a minute.
draw.io - Online diagramming application
Immoviewer - Immoviewer is a software solution that combines Automated Real-Estate Video Content creation with simple and scalable 3D 360 tours.
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.
RICOH360 Tours - With no professional equipment or expertise, RICOH360 Tours will let you introduce and share real estate property, facilities, etc., with remotely located customers using means such as a website or through web conferencing.