It Came From Outer Space

Jack Arnold directed this 1953 film based on a Ray Bradbury story and starring Richard Carlson and Barbara Rush.

Aliens land on Earth to make repairs to their ship and try to pass as humans. Surprisingly good for its time with good performances and a tense storyline. And who doesn't love alien movies?

http://www.imdb.com/title/tt0045920/

This Island Earth

This movie scared the hell out of me when I was a kid.

Surprisingly good sci-fi flick from 1955 directed by Joseph Newman stars Jeff Morrow, Rex Reason, and Faith Domergue.

Earth scientists are recruited to work on a secret project. Unbeknownst to them, their employers are aliens who communicate with their planet through a device called an Interossiter. The scientists are eventually abducted to the aliens' home planet where they help their abductors fend off other maurading aliens.

Suspenseful and quite elaborate special effects considering when it was made.

http://www.imdb.com/title/tt0047577/

Fire in the Sky

A different kind of UFO movie for sure.

Supposedly based upon a real incident, Fire in the Sky was made in 1993, directed by Robert Lieberman, and stars D.B. Sweeney and James Garner.

Loggers see a strange sight in the woods and drive off, leaving Sweeney behind. When they return, he is gone and stays missing for five days. The loggers are suspected of committing murder and James Garner investigates. Plot turns around when Sweeney reappears and claims he was abducted by aliens.

Provoking, dramatic effort is not great but interesting.
http://www.imdb.com/title/tt0106912/