I'm sorry to see that Majel Barrett Roddenberry died of leukemia this morning, age 76.
Memory Alpha's entry says that she was "the only performer to have had a role on all of the Star Trek series": as Number One in the original series pilot, as the voice of the Enterprise computer in many contexts, as Lwaxana Troi, and as various other characters.
She's reprising the ship's-computer-voice role for the new Trek movie; the abovelinked article says she completed recording for that a couple weeks ago.
She also (I don't remember whether I knew this) played the widow of the Centauri emperor in Babylon 5. Plus a character in the animated Spider-Man TV series in the mid-'90s, plus many other roles in other shows and movies.
And she was executive producer of Earth: Final Conflict and Andromeda.
I think of her as one of the main people who kept Trek going all these years, but I don't know whether that's really true or not. Regardless, she certainly contributed a lot to the various shows and movies.