blog.arduino.cc:

Arduino Yún is the combination of a classic Arduino Leonardo (based on the Atmega32U4 processor) with a Wifi system-on-a-chip running Linino (a MIPS GNU/Linux based on OpenWRT). It’s based on the ATMega32u4 microcontroller and on the Atheros AR9331, a system on a chip running Linino, a customized version of OpenWRT, the most used Linux distribution for embedded devices.

Available at the end of June for $69.

• MCU – Atmel ATMega32u4 @ 16 MHz (same as the one used in Leonardo board) with 2.5KB SRAM and 32KB flash

• SoC – Atheros AR9331 MIPS-based Wi-Fi SoC running Linino, Arduino’s own Linux distribution based on OpenWRT. It’s the same chipset as in TP-Link WR703N router.

• Storage – microSD card slot

• USB – micro USB connector + full USB host port

• Connectivity – Ethernet + Wi-Fi

• 14 digital input/output pins (of which 7 can be used as PWM outputs and 12 as analog inputs)