Joomla templating tutorials.
Good basic sessions (explaining what modules, components, plugins are and how to add content, menus and modules based on menus etc)
http://www.screentoaster.com/Then template tutorials. There are a series of videos - creating templates from scratch - 4 videos, Modifying existing templates - 4 videos. These videos include some basic instructions to use firebug etc. Very useful for novices and might be a bit boring for advanced users. However they explain joomla templating very well.
http://www.youtube.com/user/
Video tutorial on creating a module in Joomla.
Excellent documentation on Joomla templates and Component creation. I recommend to go through videos and then through this documentation.
