asciiflow - Infinite ASCII diagrams, save to Google Drive, resize, freeform draw, and export straight to text/html.
Superdocu - Onboard people at scale, stay compliant.
Core2D - A multi-platform data driven 2D diagram editor.
Quick Diagram - A tool for generating diagrams and flowcharts from text.
JavE - JavE (Java Ascii Versatile Editor) is a free Ascii Editor.
draw.io - Online diagramming application