I've read about Canny, but it doesn't seem to enjoy a lot of versions or 
users since it's been released.  I've read that Ruby natively supplies 
template functionality.  I need to know how easy it will be with Ruby to 
re-skin a webapp.  Also, whether Ruby or Ruby on Rails would be 
preferable in this situation?

Note, I'm not looking for simple JSP functionality, but the ability to 
go beyond that by having Ruby select a specific template at runtime, the 
way I can do with Smarty.  I want to abstract the template away so that 
the end user will get the same URL regardless of the skin that's used to 
display it.

I'd appreciate whatever advice you can give.