This Chrome extension lets you compose emails in Markdown, and then convert it to HTML to use in Gmail. Gmail doesn’t offer you much in the way of formatting to make your emails look more attactive.

The free and fully-featured Markdown editor for Windows allows you to write using an easy-to-read, easy-to-write plain text format, and then convert it to structurally valid XHTML (or HTML). In short, ...

You can use HTML elements to format text in various ways; for example: Bold text using <b>. Indicate strong importance, seriousness, or urgency using <strong ...

I suppose you already know what Markdown* is. For those who don’t know, let’s quote a few paragraphs from John Gruber’s Daring Fireball: Markdown is a text-to-HTML conversion tool for web writers.