I've been messing around a little bit over the past few weeks with the Web site ManyEyes, a project of IBM. It's intended to let people visualize data, and one of the things it lets you do is upload a piece of text (like a speech) and map it out.
I went over there, and someone had already uploaded the text of the "I Have a Dream" speech from 1963, which CNN just replayed a little while ago. Below is an interactive of how Many Eyes charts it out, using "dream" as the keyword.
ManyEyes is free to use. Go over there and have some fun.
