It’s a screensaver for Mac OS X that hooks into the Instagram API and grabs a feed of photos – either the ones that are most popular across the service, or just the ones your friends share with you.
Every time your Mac is idle, you’ll be treated to an ever-changing animated display of instafun from all your instabuddies. Here’s a video of the screensaver in action:
Oh, and it’s free. You can say thanks to Doug Pfeffer.