The RPi Relay Board gives your Raspberry Pi the ability to control high voltage/high current devices, easily makes normal home appliances become intelligent.

RPi Relay Board Features

• Supports Raspberry Pi A+/B+/2B/3B
• High quality relays, loads up to 250VAC/5A, 30VDC/5A
• Photo coupling isolation, prevent interference from high voltage circuit
• Onboard LEDs for indicating relays status
• Relay control jumper, allows to control the relays by custom pins other than the default pins
• Comes with development resources, including examples in wiringPi, WebioPi, shell, python, and bcm2835
   

• Wiki