This Perl module, available from CPAN, is what Apache::MiniWiki uses to render pages. It does a pretty decent job of converting Structured Text into a format that looks good in a browser using HTML.
You can check out the docs at http://search.cpan.org/author/GDR/HTML-FromText-1.005/FromText.pm
Version 2.0 is a total rewrite of the module, but is supposed to be backwards compatible.
Read the edit page to learn how to write with the Wiki syntax, which is really pretty simple.
A similar module is Text::WikiFormat.