David Fowler of uC Hobby writes:
A new version of the Arduino board was released that added a cool new feature. With help from Paul Badger of Modern Device Company and Brian of the Freeduino project this article will show you how to modify the Bare Bones Arduino board to make it compatible with the new Diecimila Arduino. No more pressing the reset button to load your code and no more long waits to see if it runs.
Bare Bones Arduino Diecimila Mod – Link
BTW, you can also modify an Arduino NG or serial board to automatically reset when you upload a sketch. See: this post on the Arduino blog for details.