Wow. Thanks all - That's all just a little over my head at the moment, but I think I'll get there soon.
A bit more info about the project would maybe help. You say to raise/lower 64 objects of about 5KG weight by about 25mm but will the movement be either fully up/down or can it be any position between. Also how fast must it raise/lower.
Sorry Riva - I was a bit vague! Yes, I need to raise/lower the objects by a discrete (measured) distance rather than just all the way up or down, although the speed of movement is quite inconsequential - I'm moving a series of lights and mirrors and other objects in response to infrequent changes in the environment. Nothing needs to happen particularly quickly. Accuracy is the most important thing.
I had a read of that arduino playground article and some other info about the ATtiny85 - sounds promising to me (although at the moment I have no idea what communication protocol that motor controller I linked to uses - can anyone point me in the direction of something useful??).
The other thing that came to mind, rather than using ATtiny85s, was having some kind of ICs that could be allocated an address number using a series of DIP switches or hard-wiring, and which only allowed messages corresponding to their hard-programmed address number to pass through to the motor controller. Does such a thing exist? If so, can anyone let me know what it might be called?
Thanks for the ideas! This is starting to look a little less impossible....