asciiflow - Infinite ASCII diagrams, save to Google Drive, resize, freeform draw, and export straight to text/html.
draw.io - Online diagramming application
Lekh Diagram - Lekh Diagram empowers you to express your idea on iPad and iPhone simply by sketching shapes with...
Automatic Organizational Chart Generator - Turn your Excel employee list into an Org Chart with Photos!
Core2D - A multi-platform data driven 2D diagram editor.
LibreOffice - Draw - Draw, LibreOffice, ODF, open standards, creative software, vector drawing