Markdown is a text-to-HTML conversion tool for web writers, allowing you to write using an easy-to-read, easy-to-write plain text format, then convert it to structurally valid XHTML (or HTML).
Althought I prefer Textile for its table support and other niceties, Markdown makes for slightly more readable text when writing essays.
Implementations:
| Date | Link | Notes |
|---|---|---|
| Oct 16 | Pandoc | A markup converter written in Haskell with support for it |
| Older | WMD | an amazing JavaScript editor specifically tailored for using Markdown. |
| Make.text | a bookmarklet for translating a web page into Markdown | |
| PyMarkdown | for Python, obviously. | |
| python-markdown2 | a second Python implementation, with some improvements. | |
| BlueCloth | for Ruby | |
| PHP implementation | ||
| C# / .NET implementation | ||
| Partial implementation | in JavaScript | |
| Showdown | a better one | |
| A more complete list | maintained by François Granger, who is developing a markup converter. |