At Freedocumentaries.org you can stream interesting and provocative documentary films for free.  These are largely political or social documentaries, and vary in quality and length.  There are many smaller videos but there are also television series and wide release movies too (eg. Manufacturing Dissent and Sicko).  Subject areas covered include the environment, animal rights, human rights and health, as well as the required 911 and GWB doccos.  Certainly worth a look!
http://www.freedocumentaries.org/index.php