PBS currently has fifty-four complete Frontline programs freely-available for streaming on their website. The 2006 releases available include: The Insurgency, The Meth Epidemic, and Country Boys.
Frontline World is considered a separate series and that too has many programs freely-available online - about seventy currently. 2006 releases include Columbia: The Coca-Cola Controversy, Brazil: Jewel of the Amazon, Iraq: Saddam's Road to Hell, Pakistan: Cold Comfort, and India: Calcutta Calling.
Frontline World link