Some people says that i write too much!!!!!
Well, joomla is a great tool for beginners. i personally works in joomla but it is difficult to find a good template for free and it is really hard for a developer like me to work on joomla template. so i choose joomla template frameworks to do the job.
Now you know that the benefit of using open source software is the flexibility of choosing a lot of options. so there are a lot of template framework in joomla. but i think (as my senior in the office faruk vai says) the most popular is Gantry framework. Another one is JA Template framework from JA Team.
Here are the links:-
Gantry framework download page:- http://www.gantry-framework.org/download
JA Template framework download page:- http://wiki.joomlart.com/wiki/JA_Template_Framework/Overview