As noted in passing in another post, I'm writing a library (like  
RedCloth) for turning a specific text markup syntax into HTML/XML.  
OWLScribble is this work in progress, and it's working pretty well  
right now!

For information on the markup syntax itself:
http://phrogz.net/RubyLibs/rdoc/OWLScribble/markup.html

For information on using the OWLScribble class:
http://phrogz.net/RubyLibs/rdoc/OWLScribble/doc/index.html

 From the intro documentation:

"OWLScribble converts a specific set of text markup into HTML. (The  
syntax used in the markup is a knockoff of the markup used by  
OpenWiki, so the ┴░WLin OWLScribble means "OpenWiki-like".)
The tree of elements created during parsing is made available, along  
with collections for specific types of elements, such as a list of  
all wiki-commands or wiki page links. This lets you modify the  
element tree (e.g. perform a database lookup on pages and replace the  
links with html anchors to your URL) after parsing, but before  
creating the HTML string."

I'm not yet cool enough to know how to make this into a gem. I hope  
to do that in the next week or so as I get near release quality.  
(Right now, there aren't enough unit tests for me to feel good about  
calling this ready for the wild, and there are a couple minor tweaks  
I may want to make to the markup syntax.)

I certainly appreciate all feedback -- positive and negative --  
regarding the quality of the documentation, efficiency of the code,  
or features/interface in the class.

--
"When I am working on a problem I never think about beauty. I only  
think about how to solve the problem. But when I have finished, if  
the solution is not beautiful, I know it is wrong."
- R. Buckminster Fuller