I designed the Arduino Runtime board. The idea is to have a standalone Arduino, but in a PCB format, so I don't need to wire all the cables in the breadboard or proto PCB board every time I need to deploy a project.
1) Size: It is just 62 x 39 mm 2) It uses a ceramic resonator, instead of a crystal (same 16 MHz) 3) Digital I/O pin is breadboard friendly and I added a +5V pin in the same row 4) I added plenty of Ground pins 5) ISP or ICSP port 6) Optional power supply circuit, with DC input jack (actually, except for the ATMEGA8/168, one 0.1uF cap, one 10k resistor, a couple of header pins and the ceramic resonator, the rest of the components are optional). 7) Eagle files published (coming soon in another post) 8) Low cost 9) Tested (one of the pictures show the Arduino Runtime Board running the Knight Rider 3 in a bread board)
Pictures of the board: