I like cheat sheets. They give a birds eye view of the whole picture. Cheat sheets are also massive time savers in that, you don't have to pour over reams of content to find what you want.
A self confessed convert to Ubuntu, Raphael has put together a nice cheat sheet for beginners in Linux, which explains all the important Linux commands in a clear manner.
The cheat sheet contain basic commands for process management, creating user accounts, archiving data, basic terminal shortcuts, file manipulation, and regular expressions, just to name a few.
You can download the cheat sheet at the following link [PDF].