While I hear a lot more talk about the Raspberry Pi and Arduino, these BeagleBoard products are what I want to use for any embedded or small hardware development (in my case, a custom scientific instrument).
This latest BeagleBoard-X15 comes with 2 Cortex-M4 microcontrollers and 4 PRUs (small realtime microcontrollers) on the board with a decent computer. That's a great set of tools with none of the fussy wiring problems of using multiple Arudinos.
If the X15 has enough discrete microcontrollers for the job, then there's a huge advantage in using it: you get to wire your major components together with software, not harder. Every time I find a way to shift a problem from hardware in software, I get more productive.beagleboard.org/x15