I saw this in the nanode irc channel:

I've never seen any real world projects with MQTT... it looks good though.

So I'm looking for real world projects that use MQTT. If you've got a project it'd be great if you could mention it in the comments. A short sentence on what it does and how many clients you run on it - really anything you can say. If it's a secret please still comment if you can, just be very very vague. If you've got a blog post describing it, link that instead. I'm interested in everything from a single temperature sensor reporting to a computer up to millions of mobile users.