I was frustrated with the way current Pi-to-breadboard adapters take up the middle bridge on a breadboard, reducing the space available for prototyping. I made an adapter board for 40 pin Pis that solves this problem by taking the double stacked, 2x20 configuration, and breaking it out into a more accessible single 1x40 column.
There's female header on the left side to plug in a 5V regulator board. Although the PCB extends further down the breadboard, all pins on the Pi now have access to both sides of the breadboard :)
Here is the first revision board powering an A+ with a screen from Adafruit. The first switch applies raw 12V DC power to the 5V regulator, and give the user access to 5V and unregulated DC terminal blocks. The second switch applies 5V to the Pi and allows access to the Pi's 3.3V at its respective terminal blocks.
Here are the first and second revision boards side by side. Unlike the first board, the second revision's switches sit flush with the board.
If you would like one of these boards, zing me some email.