Just wanted to share my last design called µHost, a minimalist Arduino compatible board to host your Arduino projects when budget is very tight - and you don't need the fancy USB compatibility to run your design!
Main characteristics: - Arduino UNO REV3 pinout, plus peripherals such as voltage regulators and pin 13 LED, for maximum compatibility with the existing Arduino shield ecosystem - mixed CMS and THT component footprint to be able to install the board with whatever component you have in your DIY electronics personal collection, - Standard 5x5cm frame compatible with generic low cost PCB pool services, - programming via ISP thanks to another Arduino board, or ISP programmer (No USB capability)
The concept beyond µHost is to have a minimalist Arduino compatible setup for DIY projects without the need of a full featured, USB enabled, generic Arduino board. Take that PCB, populate the components you need to run your minimalist Arduino setup, plug your shield on it, and you're good to go!
And yes, using it is really cheap: if ordering online via a low cost PCB pool service with parts aside, board pricing goes below 5€ per board when building a batch of 10 boards. That's really worth the deal when you are dealing with instancing multiple boards on an application without the need for USB capability!
It's been a useful tool to bench stuff and make standalone geeky toys at home. Hope you'll find it useful too!