SketchUp - 3D for Everyone
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.
SketchBook - SketchBook is a professional drawing or painting application that allows designers, architects, and concept artist to sketch their ideas and create adorable illustrations in no time.
draw.io - Online diagramming application
ActCAD - ActCAD is one Software for many applications covering the primary domains of – Architecture, Engineering, Construction (AEC) including Structural, Electrical, and Mechanical.
Visio - Simplify and communicate complex information using data-linked diagrams.