There.com
Got a scoop about this organization from none other than the Change Agents solo Puppetmaster, Dave Szulborski. Dave writes:
They are a company quietly developing ARG games professionally, using people who have real experience from but not limited to Majestic etc. Check out [their] website. They've recently conducted a small beta test of sorts – check out this page.
We're looking forward to hearing more about this effort.