Pi Zero - the $5 computer

I'm not personally buying it, but it also doesn't seem like a huge waste of money either if you wanna get into figuring out ARM systems on GNU/Linux, or maybe Android.

Definitely not freedom respecting though. This comes from a guy who's used the regular RPi. VideoCore IV still uses proprietary firmware, even if they freed the drivers. At least all you need is the KMS graphics drivers to get graphics to work on Wayland. Yeah, screw using Xorg on ARM devices. I always seem to run into a situation where I need the X-specific drivers for the GPU hardware, and that's really annoying.

Maybe a better choice than the Pi Zero would be one of those trusty Beagleboards or Cubieboards that lots of people talk about. I think you can use a mainline ARM kernel, or Linaro kernel, on the CubieTruck.