Jan Henrik wrote this Instructable detailing the build of his PWM generator and servo tester with ATtiny45:
This PWM generator also works as servotester, it supports all kinds of servos, which dont need more then 5V
Features:
Operating voltage: 5V
Max PWM current: 1 A
PWM frequency (by now) : 500HZ , I am trying to make that changeable, if you know how, let me know :)
High effency
small size
small prize ;)