Arduino-Uno R2 is a micro-controller board and has fourteen IO pins which may also be used as PWM outputs. Arduino is a good Raspberry Pi alternative
Can be connected to DC power/ battery or USB
Netduino Plus 1 Raspberry Pi alternative is open-source electronics platform with a 32bits controller and it uses the .NET Micro Framework.
Good for professional and hobbyists alike.
20 GPIOs with SPI, I2C, 2 UARTs (1 RTS/CTS), 4 PWM channels and 6 ADC channels. Code.
A much affordable single-board computer Raspberry Pi Alternatives. BeagleBone Black DevKit is suitable for all.
Same configuration as the original RaspberryPi but a lot faster with more punch.
Microcontroller board based on the ATmega328.
Good Raspberry Pi Aletrnative