Ive bin tinkering with a robotic arm i call RoboArm II for the past few months that you might want to have a look at.

Heres some pics :
http://www.geocities.com/nettron1000/RoboArmII.html

It uses various DC motors. The base rotation motor is a 24 volt gearhead, the main arm lifting motors are two 12 volt gearheads, the "elbow" motor is a 12 volt which drives a series of spurgears via a rubber drive belt and the wrist rotation motor is 12 volt worm gear type.

The parts came from various sources mostly from junk parts i had laying around or from trades i made with other builders and some came from on-line surplus outlets, so it cost very little to build ( so far).