There are tons of Arduino clones on the market that bring little more to the table than a few extra or different connectors or just a different shape. With the PCIeDuino
we see a new form factor that actually brings new functionality to the table: mini-PCIe. Now you can integrate an Arduino board directly into your single board computer. Buy on Tindie ($30 USD)
PCIeDuino is an Arduino board with a mini-PCIe card form factor. It is based on SparkFun's Pro Micro 3.3V/8MHz board, but targeted at being closely attached to the host computer boards. It's using the USB line of the mini-PCIe connector, thus it should be compatible with all common single board computers that have a full-size mini-PCIe connector.
Source: PCIeDuino via Hackaday
Learn more at: http://paxinstruments.com/pcieduino/