For anyone still looking for/needing electrically operated linear actuators, ServoCity just started carrying a new series of ball-screw actuators. These differ from ACME-screw actuators in that they have much lower internal friction, so can move faster, can carry more load. Here's the link...
http://servocity.com/html/450_lbs__t...r_actuato.html

If someone were inclined to make a giant animated whatever, this would be the way to do it. These things can move fast, and are capable of ridiculous force. Pair one of these with a Pololu JRK motor feedback motor controller, and you've got a servo that can move up to 3"/sec and push up to 450lbs!

- Hook