From Slickdeals:

Only PAID prime accounts get free movies.

1. Student, mom, and Amazon Prime member guest accounts will not work. Free trials do work.
2. Customer must be in the United States.
3. Not all TV shows and movies are free.
4. This only applies to STREAMING video. Devices that do not live-stream, like TiVo or the Amazon Unbox Player, will still pay regular RENTAL or PURCHASE prices.
5. iPhone, iPad, iPod Touch not supported.



From Amazon:
As an Amazon Student member you already receive:
FREE Two-Day Shipping with no minimum order size
One-Day Shipping for $3.99/item
Upgrade to a paid Amazon Prime membership for $79/year to also get:
Unlimited, commercial-free, instant streaming of 5,000 movies and TV shows
[Thanks WDEagle]

Amazon VOD Content:
==========
Not all titles available for instant streaming are free for Prime members. Only about 1600 movies and 400 TV shows are free

For ROKU owners, you need to add the Amazon INSTANT Channel to view the free movies and free tv shows [annamadison]

A couple existing threads on this already.

http://forum.dvdtalk.com/blu-ray-bar...ree-prime.html
http://forum.dvdtalk.com/tv-talk/587...streaming.html