I recently downloaded and decided to give a quick run to Hortonworks Data Platform (HDP) Sandbox. As suggested it takes only 15 minutes for anyone to get familiar about key Hadoop components i.e. Pig, HBase, Hive, Oozie and few others. The Sandbox comes with pre-configured and pre-installed VMWare or VirtualBox compatable VMDK running CentOS 6.2 Linux, which user can download and open very easily with any of above free application. This 15 minutes walk through checks out key Hadoop components in HDP sandbox.
If you are new to Apache Hadoop, this is the easiest method you have to get familiarize yourself with Amazing world of Hadoop.
HDP Sandbox Instructions: http://hortonworks.com/blog/hortonworks-sandbox-the-fastest-on-ramp-to-apache-hadoop/
HDP Download Links: http://hortonworks.com/products/sandbox-instructions/
VMDK Username and Password: root/hadoop