The program above does the exact same thing, but I like the visualization the best of the applications out there. I think I used to use Treesize but moved to Scanner because it works so well. I love the graphical representation as a pie chart. I can then click on any of the blocks and that block becomes the gray circle in the middle with the files/subfolders filling the pie chart around it.

But neither of these programs could really do what I was looking for, which was tell me what was changing. I knew that gigs of data was being added every so often, I just didn't know where. The above solution was the most elegant I could come up with.