This is a design for an open-source prototyping shield for Arduino NG/Diecimila. It has tons of cool features, to make prototyping on your Arduino easy.
Features
Reset button up top
ICSP header
Lots of GND and +5V rails
DIP prototyping area makes it easy to add more chips
SOIC prototyping area above USB jack for up to 14-pin SOIC chip, narrow medium or wide package.