Although others may have their own opinions, I think that for so many servos you should offload that part of the work to a dedicated controller like this:http://www.lynxmotion.com/Product.aspx?productID=395
Controls up to 32 servos, takes commands over serial.
Keeping 24 servos updated will eat up a lot of your computational effort. Also the wiring will be messy - the SSC-32 handles the servos for you and the wiring is already dones.
Of course there is satisfaction in doing it all yourself from scratch, and if that's the way you go make sure you let everyone know how!