Here's the book that got me started, Raspberry Pi for Beginners.
While the book is chock full of RPi resources, I actually had a challenging time simply getting started. My downfall was trying to configure the SD card from a Mac. Thus, after scouring the web for additional RPi tutorials, I eventually settled on Adafruit, which has an incredibly extensive library of tutorials here.
Lesson #1 from Adafruit clearly explains what needs to be done to prepare the SD card from either Windows or Mac OS, including quick links to all the software packages. I installed Raspbian in a matter of minutes. The longest part of the process was waiting while data was written to the SD card.
The second challenge for me was finding a suitable HDMI ready monitor. While most current day monitors have built-in HDMI, older monitors do not. I had to create a work around using a DVI cable, and DVI-to-HDMI adapter in between. This didn't work on the first monitor I tried, but the boot up screen appeared on the second. For future RPi work, I will purchase an HDMI ready monitor.
Raspbian, like most Linux distros, has a very familiar feel to anyone used to Windows XP, or a Mac for that matter. There's a simple desktop with default applications like a web browser and terminal window, and a task bar at the bottom with commonly used program icons, time/date, and access to settings. This graphical user interface has become standard (discounting touch interfaces) in desktop computing. Students today using any of these operating systems (Mac, Windows, Linux) can quickly jump between them, often not even realizing they are working on a different OS.
Aside from all of the interesting physical computing projects that can be done (a la Arduino), the RPi can stand in as a versatile, inexpensive desktop computer. It is a bit slow by comparison, and I am still working to get Flash running on it, but for $35.00 it is a worthy alternative. For now I am using it as a second computer, exploring the Pi store, and getting to know Python. As you can see from the photo above, I decided to laser cut a box for it. Thanks again to Adafruit for the Pi box template.