When Raspbian Jessie was launched a week-and-a-bit ago, included in it was a new version of Scratch. In addition to an overall improvement in speed/performance, native GPIO support was introduced as well as the ability to control the Camera Module. This means that users now have an ‘officially supported’ way of integrating physical hardware using Scratch on the Pi. As well as basic GPIO control, several add-on boards have been integrated to make it easy to use them. You can read the official announcement from the Foundation here and you can see examples of the new commands available here.
I’d like to add my voice to the thanks to Simon Walters who wrote ScratchGPIO, which was what everyone used before this new version of Scratch was announced. This was a revolutionary way of using Scratch and GPIO together for the past few years and he was always willing to do things like add new add-on boards into it and improve the user experience. Here’s hoping that the new version will receive similar support!