This is a design for an open-source prototyping shield for Arduino Uno NG, Diecimila, Duemilanove. It has tons of cool features, to make prototyping on your Arduino easy.

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.
A 'mini' breadboard included
Extra 6mm button