In addition to the other videos above, heres a video guide for the gaps in Freedom Plaza. You can find it below.
Also, here's the link to a forum on various gaps and locations.http://forumsarchive.xbox.com/PrintPost.aspx?PostID=16340913
You might need to sign into your microsoft account to access the written guide. I personally find video guides to be more helpfull, but the forum is good for more information on a certain gap if it's on the forum.