Join a local or regional screenwriters group. These groups often have online sites filled with useful information. A number of locales have screenwriters groups designed to allow writers to network and read one another's work. Consider starting a group yourself if one does not exist in your area.
Sign up for an online screenwriting forum such as Done Deal Professional. In addition to the resources that this particular site offers for a fee, Done Deal Professional offers free information on both the business and craft of screenwriting, including discussions of both produced and unproduced scripts. The site also offers an opportunity to read pages from other site members' screenplays.
Visit a website such as Simply Scripts or Drew's Script-O-Rama. Both these sites -- and others like them -- provide free links to screenplays.