Python templates for web designers
I've played both roles and at heart I prefer more of a programmer's templating language. However, I freelance for a few graphic designers doing the "heavy lifting" backed and db programming and can tell you that I've had the best luck with XML templating languages (SimpleTAL, Genshi, etc). 
When I'm trying to be web designer friendly I look for something that can be loaded into Dreamweaver and see results. This allows me to provide all the hooks in a template and let the designer tweak it without worrying about breaking what I've already written. It allows us to share the code and work better together where we're both comfortable with the format. 
If the designer codes without a WYSIWYG editor, I think you're options are less limited and you could go with your own personal favorite.
What are some good templating engines for web designers?  I definitely have my preferences as to what I'd prefer to work with as a programmer.  But web designers seem to have a different way of thinking about things and thus may prefer a different system.
So:

Web designers:  what templating engine do you prefer to work with?
programmers:  what templating engines have you worked with that made working with web designers easy?