Kurt over at the Open Hardware hub has published details of an interesting and different type of circuit - an Arduino hard-reset system. The purpose of this is to allow an Arduino sketch to actually reset the board it is running on. Great if you just need to start a sketch again from a deep point in a sketch (shades of GOTO...) or have intelligence to detect when a situation cannot be backed out of and need to restart the system. It operates with one digital pin which triggers a 555 monostable circuit that holds the reset pin HIGH for a moment - thereby resetting the Arduino. You can make your own using Kurt's instructions and EAGLE files, or add the circuit to a protoshield.
When making your own reset circuit, you'll need a protoshield to mount the external circuitry. In doing so, consider our range of ProtoShields. From the tiny LeoStick to the Mega range, we offer a complete range for you to work with.