And for everything else, there's AsciiDoc.[0]

For an extra five minutes learning you get a boatload (think container ship) more features[1] - it compiles to DocBook: a mature, actually standardised, highly structured format, and from that you get HTML, EPUB, PDF, slideshows, and man pages for free.[0] For math you get MathML, ASCIIMath, and LaTeX (along with a number of ways to render them.) It has a super nice syntax, is equally good at little docs and huge books, and you could theoretically write a proper academic paper in it with the LaTeX backend. And you always know what's going to happen when you try to mix bold and italic...

Also endorsed by Linus.[2]

    [0]: http://www.methods.co.nz/asciidoc/#_overview_and_examples
    [1]: Well, five minutes to be able to do everything Markdown can do; everything else will take a bit longer
    [2]: https://plus.google.com/+LinusTorvalds/posts/X2XVf9Q7MfV (comments)