asciiflow - Infinite ASCII diagrams, save to Google Drive, resize, freeform draw, and export straight to text/html.
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
JavE - JavE (Java Ascii Versatile Editor) is a free Ascii Editor.
LaTeXDraw - LaTeXDraw is a graphical drawing editor for LaTeX.
Charaster - Open-source ASCII art editor for browser-based, raster-style editing
Ipe - Ipe is a drawing editor for creating figures in PDF or (encapsulated) Postscript format.