Microsoft Popfly looks more like an experiment than a website that allows you to build websites with little or no programming skills. Maybe it's a little of both.
I like the concept - a lot - and encourage you to check it out. You have to register to play and you need a Microsoft Passport account to register (but seriously, who doesn't have an MS Passport account these days?).
Something to note: Adam Nathan, author of one the coolest new books about WPF (Windows Presentation Foundation Unleashed) is one of the members of the development team.
Also note the domain extension ".ms" belongs to the island Montserrat, famous for Beatles producer George Martin's recording studios until a volcano closed the capital, docks, and aforementioned studio in 1995 (I love wikipedia!).
Technorati Tags: Popfly Microsoft Nathan Developer Community