Smashing Magazine the online resource for all types of stuff has a post pp called:

It’s a nice post listing most of the Joomla resources you’d end up encountering while development a Joomla site. Here’s a quick excerpt from the post:

Joomla is a popular free and open-source content management system (CMS) that can be used to power all kinds of websites. After we published developer’s toolboxes for a variety of other CMS’, many readers requested a collection of resources for Joomla users and developers, so here it is.