Star Trek

Star Trek is one of the most famous science-fiction continuua. It was created by Gene Roddenberry. The basic premise is that in the future, Earth and a number of other planets form the Federation, with a military/exploration arm known as Starfleet. Most of the series feature a crew of humans and other creatures on an exploratory vessel, charting unknown space, aiding those in danger, and getting into scientifically slightly-implausible but very exciting scrapes, from which they always escape narrowly.

The Original Series
This starred William Shatner as Captain James T. Kirk, with Leonard Nimoy as Spock, voyaging on the starship Enterprise.

The Next Generation
Patrick Stewart stars as Captain Jean-Luc Picard of the starship Enterprise (the fourth or fifth vessel to bear this name since the days of the now-legendary Kirk).

Voyager
Kate Mulgrew stars as Captain Kathryn Janeway, of the scout starship Voyager, which is catapulted to the Delta quadrant and must make its way home over unimaginably vast distances.

Deep Space Nine
The only series not set on a ship; this follows the adventures of the crew of the space station Deep Space Nine.

Enterprise
A prequel series, set before the time of Kirk.