I went to Presenting Data and Information yesterday, a one-day course taught by Edward Tufte.
The course was based on three of his books (Envisioning Information, Visual Display of Quantitative Information, and Visual Explanations), each of which we received copies of. (I had all three signed along with the poster).
The course was incredibly interesting - particularly relevant for technology and law, two fields that deal with communicating great amounts of information and data. The session about the evils of PowerPoint was enlightening, and his points were nicely illustrated in the entertaining rendition of the Gettysburgh Address, PowerPoint style.
I'm going to reserve comment on the actual material until I have a chance to read and digest the books.
If you have the opportunity to see attend one of these courses in the future, I would highly recommend doing so. More information and schedule here.