BeagleBone Black: The Sub-$50 ARM Linux Board
This AM335x 1GHz ARM Cortex-A8 development board with 512MB of RAM and 2GB eMMC on-board flash also has a microSD slot, a single USB 2.0 host port, a mini-USB 2.0 client port for power (or a +5V DC jack), one 10/100 Ethernet port, a debug serial header, and microHDMI for video output. The graphics support up to 1920 x 1080 at 24Hz. The SoC relies upon PowerVR SGX530 for its 3D graphics, which will immediately frighten most Linux desktop users due to the lack of open-source support and working PowerVR blobs can be hard to come by for different configurations.
Over the original BeagleBone, the Beagle Bone Black Edition runs at 1GHz compared to 720MHz on the earlier version, the original BeagleBone only had 256MB of RAM and only a microSD card with no eMMC, and did not have any video output support.
The BeagleBone Black shipped with Angstrom Linux on its 2GB eMMC storage. Aside from the embedded-focused Angstrom Linux, there's also support for Android and Ubuntu on this ARM development board plus there's been spins of Fedora Linux and other ARM Linux distributions for this sub-$50 ARM board.