The Arduino Protoshield is a Shield board that sits on top of a standard Arduino board.  More information.

This design has a few good features:

• power busses for +5V and GND in middle of board
• central bus can be configured to carry +5V, GND, neither, both (jumpers)
• Special horizontal 5-pin bus to install pin headers for external connections.
• 2x5 IDC connector area for external connections.
• holes connected in groups of five, breadboard-style
• all regular Arduino pins accessible on top
• bottom of board cannot short to USB connector as in other protoshield designs
• power LED and reset button on top
• USB/External power jumper accessible with protoshield installed
• low parts count: only one capacitor, a resistor, and LED and a switch, in addition to header pins.
• two ways to use it: add header pins and a breadboard on top, or just use through holes to wire point to point.

Arduino Protoshield PCB
Parts	Qty	Device
PCB	1	Arduino Protohield PCB
Digital header	4	4-pin long legged female header. Some kits include 2 x 8-pin headers instead of 4 x 4-pin headers
Analog/Power header	2	6-pin long legged female header
Reset	1	Tactile switch
Resistor	1	330ohm or 470ohm resistor
Capacitor	1	0.1uF ceramic capacitor
Selector header	1	6-pin male header
LED	1	3mm LED
Selector jumpers	2	Jumper or shunt
ICSP header	1	2x3 6-pin long legged female header

Special features explained

Assembled

PCB routing