I’m starting to use Markdown for some README and INSTALL files of a few of my open source projects, like PBooks. Its a nice simple language that allows an author to format a document that looks good in plain text and can be easily converted to logical HTML markup.
It comes as no surprise that Markdown is also used for some blog engines, even the one that powers this site: MovableType Open Source (MTOS). However, considering how nice the rich text editor is in MTOS, it seems more appropriate for wikis which benefit from and are seemingly powered by really simply syntax. Strangely, Markdown lacks the basic wikilink syntax. Ikiwiki has something like that, so I’ll have to investigate there to find out how they specify it.
Really, my only problem with MTOS is the template formats and rendering process. I really wish it used XSL instead.