I made another visit to the site of the old Yankee Stadium today. Demolition has progressed quite a bit in the four weeks since I visited last. The majority of the back "bleacher wall" has been torn down, so you can get a unblocked view into the stadium now. Unfortunately for me, the Manhattan bound #4 train platform was closed so I couldn't get any shots straight into the park.
They seem to be shearing the upper deck concrete into small sections that can be removed individually. I didn't see any demolition in progress, so I'm unsure what they are doing exactly. Although demolition is progressing well, I do expect some part of the stadium to be standing on Opening Day. With that, baseball fans should be able to get at least one more glance at the old ballpark.
You can see full size versions of these two photos and another 29 shots in the Yankee Stadium Demolition section of StadiumPage.com.