Ejberg.dk has developed this project for a simple ATtiny2313 based servo tester.
This device lets you test servos by varying the pulse width between limits of 0.8000 ms and 2.2000 ms selectable through the use of four buttons.
While the schematic shows an Atmel AT90S2313, the circuit will work with the popular ATtiny2313 using version 2.05 of the code downloadable from the ejberg site. He also has another version of this tester known as the ServoTester2 which uses the ATmega16P.
ATtiny2313 based servo tester - [Link]