If you enjoy photographing rapidly-changing subjects and don't have lightning-quick reflexes, you'll need to create a device that can react and control your camera's exposure. One simple way of doing this can be done based around an Arduino board, and Instructables user "geo bruce" has documented an excellent way of doing so that makes the following type of image a possibility:
His system is based on a laser diode beam, and could be modified for other types of subject. The required external circuity is simple to assemble, and the use of an LCD module keeps the user interface user friendly. To find out more, check out the details from here. And for more, we're on twitter and Google+, so follow us for news and product updates as well.
If you're interested in adding a user-interface to your Arduino projects, or just need an LCD - save time and move forward with the Freetronics LCD & Keypad shield which contains a bright 16x2 character LCD and five buttons that can be read from only one analogue input pin: