> I'll probably just code a wrapper function that parses the URLs after
 > markdown did it's thing.

Try the auto_link() helper method:

http://api.rubyonrails.com/classes/ActionView/Helpers/TextHelper.html#M000426

I noticed this today while reading through the docs on helper methods. 
There were quite a few I didn't know about.

--
John Long
http://wiseheartdesign.com