If you are just digging in, many resources are available to help you. I suggest you start with these:
Apache is the owner of the Hadoop project. Hortonworks and Cloudera are currently the top 2 vendors who provide a distribution of the Hadoop software.
These books have been very helpful in getting up to speed with Hadoop application, concepts and support:
Another company in the big data space that you should take a look at can be found at http://pivotal.io. Pivotal is combining Hadoop with the Greenplum database clustering technology to interesting effect, with a focus on Platform as a Service (PaaS).