Long story short, I need to get up to speed with Joomla fast. I only have this weekend to do that which translates to about 12 hours of time. Right now I only know that Joomla is an open source CMS written in PHP. What would be the best way to familiarize myself with Joomla in this short amount of time? Official documentation? Videos? Books?
My background: I think I have a fairly decent knowledge of PHP and I'm currently learning CodeIgniter while building a simple webapp with it.
Since you do not have a book yet and you must not loose time Google this "Joomla Quick Start" and you'll find a few interesting links.
Also, here is a Joomla Quick Start, in PDF format, from Joomla web site, that you can start reading right away.
Good Morning,
there a plenty "free" books on Google Books with lots of information!
Joomla building a Successful Site / Joomla visual Quickstart .. try it by your self Google Books Joomla
If you need to do templates have look at this post and my answer.
How should I go about writing a Joomla! template?
I was in a similar situation. I purchased "Joomla! A User's Guide: Building a Successful Joomla! Powered Website" by Barrie M. North. This was big help.
Next, I'd start out with some really good Joomla templates that were created by others. I like to learn from example, so here are the good examples I'd recommend.
Beez: is a free XHTML/CSS template that comes with Joomla. By default, Joomla uses TABLES for many of its modules and components. Thankfully, Joomla Overrides let you, well, override those ugly outputs with cleaner markup. Beez will show you how to do that and is even good enough to serve as your base.
Compass Designs: is the home of Barrie North, the book I recommended. He has several free templates and tutorials.
YOOtheme: Will cost you something, but you will get both good example templates and some handy AJAX tools to use as Joomla Extensions.