To learn the basics of Joomla, I strongly recommend the following tutorials:

Administrator area tour for Joomla! beginners
Part 1 of 2 (User Manager, Media Manager and Menu)
by WebWorksKC

http://www.youtube.com/watch?v=SKzesoalhYU

Administrator area tour for Joomla! beginners
Part 2 of 2 (Articles, Components and Modules)
by WebWorksKC

http://www.youtube.com/watch?v=uIAIb3gQbQk

Another great way to learn Joomla is by having the tutorials right in the backend of your website. So when you get stuck, just click on the tuturial button and learn about what to do next. The OS Toolbar extension is $49 but well worth the investment if you are new to Joomla. The guys at OS Training are awesome. In fact, that's where I first learned Joomla.

To get the OS Toolbar extension, follow this link then choose Joomla and OS Toolbar.