I heard through reddit that they were building "The Avengers" sets on 40th and Park in NYC today. Since I was already on my way to Grand Central, I thought I'd swing by and see if I saw Joss Whedon. They were still painting the set when I got there, so it wasn't ready for filming or anything. But it was kind of cool to watch. It's neat to see how much work goes into these things.
It appears to be some sort of crash site.
I also took a photo of the no parking notices. I know they have to put these out when they film in NYC. It's supposed to say what the project is and when they will be working there. I noticed this one said the Project name was "Group Hug." That made me LOL. I'll be sad if there is no Avengers group hugging now.