I did a search for Star Trek scripts and found this Index of folder at http://leethomson.myzen.co.uk/, that is just chock full of modern and retro TV scripts in an easy to browse directory. In addition to classic shows like Star Trek and Quantum Leap they also have modern shows like Dexter and Smallville. As a bonus they have a much smaller folder of TV show bibles. If you are interested in TV writing or want to look up your favorite show, it is a great source.
Television Scripts [@] http://leethomson.myzen.co.uk/