I recently started working with ARM µC, which are more complicated than 8bits µC, but they offer way more options…

• STM32F4 Discovery
• STM32F030 Nucleo
• STM32F103C8T6 Development board from eBay…
• STM32F103C8T6 Dev board as BlackMagic Probe It's basically the same hardware as the original BMP
• SparkCore STM32 µC with onboard CC3000 Wifi chip (and online/cloud Arduino-like IDE and programming process)

• Teensy3
• SWD Debug with the Teensy3/3.1
• TinyK20 BOM

• ADuC7061 USB Devstick

• Stellaris Launchpad (I think it's been renamed since I got my boards…)