Cloudera was my number one source of Hadoop information while I was working on getting my first cluster going and useful. I would highly recommend them as a resource.
I guess it depends on how you best learn. For me the Cloudera videos gave me a good overview and understanding of the various to prepare me to dig in deeper. Combined with the Hadoop book I was able to setup and run a small(12-node) cluster and use it for data storage and report generation.