Your local library can have a selection of DVD's available to borrow, usually
free. You can also usually buy cheap used DVDs, including boxsets, in your
local second-hand shop and using online classifed listings.
Also check out the Internet Archive. There's thousands of classsic movies and
videos to download or watch online, all without DRM and free:
http://archive.org/details/movies
FSF recommend www.4Flix.net for movies to download DRM free. Although I've
tried them and their SSL cert isn't valid, so the checkout doesn't work.