I enjoy using to Wikis to document all kind of stuff (recently I used MoinMoin, so I am used to that syntax).
Now I am looking for a more lightweight solution, for documents where setting up a MoinMoin server is too much hassle.
What is the "easiest" way to render a .txt file in Wiki syntax (for example by displaying it, or converting it to HTML)?
It should work on Linux, but the more platform-independent, the better.
Maybe there is even a JavaScript based solution?
Try Markdown, it's the syntax used here on stackoverflow. There's a perl tool you can download and run on your markdowned text files. Markdown is simple and intuitive.
Examples here: http://daringfireball.net/projects/markdown/basics