ASCII Art Editor

Sig Software has a cool tool, called Email Effects for creating ASCII diagrams and art.

Email Effects is a program for Macintosh or Windows which allows pictures and drawings to be used in email, source code or any other plain text medium. It is the world's premier ASCII art creator and is being used for greetings cards, signatures, program flow diagrams, maps, chemical structure diagrams, logos, and much, much more.

• Convert pictures or drawings instantly to text.
• Create text using standard Figlet fonts.
• Create exploded "big text", rotate or flip selections.
• Draw or erase lines, circles, rectangles or freehand.
• Works directly with Entourage, Outlook Express, Apple Mail, Eudora, Emailer, Mailsmith, PowerMail or QuickMail (Macintosh), or any MAPI email client (Windows).
• Comprehensive documentation and context-sensitive help.