Where can i download redhat 6 and later?

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http://www.unix.com – I have registered with redhat but unable to get the iso files for redhat 6 or later. As far as my understanding goes, Redhat desktop edition is free and they charge you for support( correct me if i m wrong). Which one is best for learning purpose? Is a choice of redhat 6 good or shall i stick with redhat 5? (HowTos)