Just stumbled across the free online course in Hadoop Fundamentals from IBM on the [urlhttp://bigdatauniversity.com/]Big Data University[/url] site. No idea if it's any good, but it might be worth looking at as a way to get started with Hadoop.
Since its free, I would definitely give it a shot.
I started the tutorials yesterday. You can pick and chose which ones to hear / read.
The tutorials do give a basic idea. So, its refreshing if you have a book along (i have the The Definite Guide) and you read through after listening to the tutorials.