This video was made by Steve Spak of the FDNY. It contains close-up shots of WTC7's infamous corner along with shots of WTC1&2's sliced core columns.
For background see:
http://www.911blogger.com/node/10295
http://www.911blogger.com/node/8788
http://www.911blogger.com/node/7471

http://www.archive.org/details/Steve_Spak_Day_Of_Disaster
Direct link to .iso image:
ftp://ia350625.us.archive.org/3/items/Steve_Spak_Day_Of_Disaster/Steve_Spak_Day_Of_Disaster.iso

PS: lots of interesting things in the archive.org footage -> http://911blogger.com/node/10284