Tess is right, the online docs are about the best to learn from as are the forums on the site for specific problems. Joomla has a pretty steep learning curve in the beginning, but it's a cool platform.
There are other CMSs out there such as CMS (cmsmadesimple.org) which are a bit easier to learn and can give you a foundation for working with joomla.
I started off my fire department's website in CMSMade Simple, and then a year later redid it in joomla mainly due to the growth of the site (400Mg).
I'm no expert in it, but i did manage to get the site up and customized so if you have any specific questions, feel free to ask
krys