WebIOPi is a web application which allows you to control your Raspberry Pi’s GPIO. Just install it on…

WebIOPi is a web application which allows you to control your Raspberry Pi's GPIO. Just install it on your Pi, and use any browser from your network. Click/tap the in/out buttons to change GPIO direction, and click/tap on each output pin button to change their state.
It's useful to start enjoying GPIOs and also to debug some circuits without writing any line of code.
It also allows to control your Pi's GPIOs over Internet, so it's a good starting point for home remote control.
You can even fully customize the included UI with few CSS modifications or use the REST API to build your own client.

Raspberry Pi’s GPIO Web interface