Another really good source of PC interfaces are Phidgets:http://www.phidgets.com/
They make a wide range of motor/servo controllers, I/O boards, and sensors that use USB or serial connections, and support a large variety of programming languages. Plus there is a TON of documentation out there in regard to them.
As far as what sort of motors and actuators you might want to use, here are some (very) general thoughts:
*Stepper motors will give you a higher degree of accuracy as far as position
have a limited range of motion unless you modify them
*Brushed/Brushless motors will give you more oomph
All the aforementioned require their own kind of controllers, and all have a different workflow. Why don't you look into some of these options and propose something? Then we can tell you what you would need to make it work, and what further things you might want to consider.