The trailers of the first three movies of the Star Wars saga is on this page. These movies made the names Luke Skywalker and Darth Vader famous. In the script plotline the first three movies made of Star Wars are actually parts 4, 5 and 6. The next trilogy (the more recent one with Anakin Skywalker) is about what happened 20 years before the events of parts 4,5 and 6.
The movies are titled:
Part 4: A New Hope
Part 5: The Empire Strike Back
Part 6: Return of The Jedi