Hortonworks, a Yahoo spinoff that offers a Hadoop distribution and commercial support services, hosts a weekly introductory webinar, Introduction to Hortonworks Data Platform, that covers topics including how to install and provision Hadoop across clusters of machines; the relationship with related Apache Hadoop projects such as Pig, Hive, Oozie and HBase; tools for monitoring clusters; and data sharing between Hadoop and other enterprise data systems.
Hadoop Essentials, a six-part recorded webinar series from Cloudera (which offers a Hadoop distribution, support and services), explores traditional large-scale computing systems, alternative approaches, and how Apache Hadoop addresses particular issues.
Sarah Sproehnle, senior director of educational services at Cloudera, also recommends another video for users interested in learning Hadoop. Introduction to Apache MapReduce and HDFS explains how the components work together to create a scalable, powerful system.
For users who prefer to start their learning with a document rather than a video, Cloudera's Hadoop Tutuorial describes the user-facing facets of the Apache Hadoop MapReduce framework.