Wondering if there are any good "open source" screenplays available on the web, ones that provide a good introduction to screenplays and have lots of "features" of screenplay writing. I would like to see the structure of them and how they are written.
Be wary of scripts downloaded from the internet, check the source. Quite often, they aren't original scripts used for submissions, but avid fans who type them up from watching the movie. As such, they could end up creating bad habits for you that aren't industry standards.
The Screenwriter's Bible by David Trottier is an excellent resource to help you with formatting.
Industry standard software like Final Draft has templates for screenplays depending on where you are submitting to, e.g. a Warner Bros standard or a BBC standard. It also has sample scripts in the Help section to give you pointers.