This extension provides support for editing files that use the Markdown syntax.  In the current version, it supports the following features:

• Syntax highlighting (for Markdown and HTML)
• A live preview window of the file you are editing
• A rudimentary margin with buttons for showing the preview window and copying the HTML-ized version of the file you are editing to the clipboard.

Here's a larger screenshot:

 

To learn more about it, see the Markdown series on my blog, or download/view the source code on github.

 

Version History:

v2.2 - Fix for utf-8 text in the preview window

v2.1 - Added .mdown, .md, and .mkdn as markdown file extensions.

v2.0 - Updated for RC/RTM.

v0.2 - Work around a bug in Beta 2 that, combined with this extension, breaks HTML files.