I bought a couple of cheap micro servos for a future Arduino project. They are impressively small (I think) whilst still delivering the torque that I require. Two are packaged in a blister pack, together with some extra servo arms and -screws.

They're called "Dynam 7g micro servo", model number DY-1002, and the specs are:

weight: 7g
torque: 1.6kg/cm (at 4.8 V)
speed: 0.1sec/60° (at 4.8 V)
size(mm): 24.3×11×19.8 mm (excl. mount points and arm)

Servos are controlled using pulse width modulation. Others described very eloquently and in great detail how this works, so I won't go into that, except for one thing, which is the point of this article: you need to know the two pulse width values that correspond to the minimum and maximum angle that the servo can be set to.

This article describes how to create a device that is triggers an external flash when an object passes through a beam of light, thus making it possible to take pictures of objects (or events) that are otherwise too difficult to capture because of their speed.

The device uses an Arduino microcontroller board which is ideally suited for prototyping, and a handful of general purpose electronic components that are fairly cheap. They are also not critical, meaning that they can be easily substituted by equivalent components.

A separate article has been written on how to set up and use this device. 

Some of the photographs I made with it are posted in the Photography section.