I wanted to see if it's possible to make an Arduino shield on the cheap 5x5 sized PCBs from Seeed so I laid out a protoshield that would fit on the 5x5 cm board.
The two rows of headers pins down to the Arduino is right at the edges of the PCB, but it fits just fine.
So it turns out that it's quite possible to use the cheap $9.90 service to do shields - if you can fit all your components within that area. Comparing a "regular" protoshield from Freetronics my boards aren't that much smaller in reallity.
KhamsaShield-1.jpg [ 181.65 KiB | Viewed 1096 times ]