As previously mentioned, today Netflix added "Star Trek: Deep Space Nine" to its online video streaming service. DS9 joins the other live action Star Trek series ("Star Trek: The Next Generation", "Star Trek Voyager", and "Star Trek Enterprise") which were added in July. Each episode streams commercial-free.
In addition, "Star Trek: The Animated Series" has been added as well. As a result, Netflix now offers the entire Star Trek TV library through it's online offering.
You can watch all of these streaming Star Trek episodes with a computer or a Netflix-ready TV, XBox360, PS3, Wii, mobile device or other Netflix-ready device. All streaming video on Netflix is shown commercial free. Streaming-only subscriptions to Netflix cost $7.99/month.