UPDATE: Play with the Processing version here: openprocessing.org/visuals/?visualID=46602
This app creates a tree as the user writes. Letters are placed around a word node, which itself is situated around a sentence node. All sentence nodes are connected at the center. I guess I could have gone for paragraphs, but that seems like it would be pushing it. The particles all repel each other, so even if several sentences wind up on top of one another, they tend to untangle themselves. The mouse has some repulsion force too, so that can be used if they get really caught.
Source Code: teaching.thesystemis.com/algo11/students/andrew/hw10/sentenceMapWallace.zip
Mac App: teaching.thesystemis.com/algo11/students/andrew/hw10/sentenceMapAppWallace.zip