The Michael Schwartz Library currently does not have a large collection scripts or screenplays. However, many screenplays are available in a variety of versions from various websites.
Scripts that are hosted online are often obtained through unclear channels, and may appear in any number of formats and versions. Transcripts are much easier to come about, and are typically just derived from the final production after the fact. A shooting script may include notes that were used in the production of the work.
You can always search for scripts that are hosted online using a search engine like Google. The most effective way would be to search the title of the film or work, and including one of the following qualifiers, script or screenplay.