Raspberry Pi is a cool low budget Linux platform. It can be used as small computer or/and project board with several available interfaces and I/O pins. Eric has been working on WebIOPi project which allows controlling RasPi I/O pins using browser.
All you need is to install small application in to Raspberry Pi and you can access pins for reading and writing using any browser on a network including smartphones. User interface is pretty simple but there is a CSS included where anyone can make modifications to make it look unique. You can also build a client using REST API. Project is still in early stage and only supports simple GPIO operations. But there are plans to add UART, I2C SPI support and more.