One popular speech synth from back in the day, I believe it was WillowTalk, had a voice called Colossus, which sounded like the voice module of the computer from Colossus: The Forbin Project. This voice was used for that of CATS in the famous "All your base are belong to us" Flash video.

Another WillowTalk voice was a clone of DECtalk's Perfect Paul good enough to be used as the voice in the MC Hawking rap recordings.

I am having a hell of a time googling for WillowTalk, do you know any links/places where I can learn more? Maybe even download something?