Variables for use in Template files?

Apologies if this has been asked before - I did search but couldn't find anything.

I notice in the template files there are variables like "", "date.year", "version" etc.

Is there a list anywhere of what variables are available? I'm toying with the idea of creating a template that will better interface with a custom Joomla PHP script, I just need to know what variables I can actually publish.

I do know that I can just export to XML and use that, but I was trying to avoid it!