Docutils and it’s reStructuredText syntax is arguably the most sophisticated of the simple mark-up to anything tools around. In the same category we find Markdown and Textile.
Docutils’ primary usage is generation of documentation for the Python programming language and projects written in same and it’s primary output format is HTML. That said docutils has been expanded greatly and has quality solutions for producing Latex, OpenOffice.org ODT, Openoffice.org ODP, pdf and WordML. The last three are available in the Docutils sandbox but are quite easy to install and have few dependencies. If you don’t want to bother with installation you can also test HTML and pdf generation from reStructuredText with the rst2a service. It even has an easy to use API.