Here are some posts I find worth reading on other graphics blogs:
Nick has done wonderful work on the evolution of the rail industry in the U.S., with a flow chart showing how mergers have produced the four giants of today, as well as a small multiples of maps showing how they split up the country.
A lovely feature of the flow chart is the use of red lines to let readers see at a glance that Union Pacific is the only rail company that has lasted the entire 4 decades, while the other 3 giants came into being within the last 20 years.
On the maps, notice a slight inconsistency between the left and right columns: on the right side, both maps have the same set of anchor cities, which act as "axes" to help readers compare the maps; on the left side, the sets of anchor cities are not identical. It would also be interested to see a version with all four route maps superimposed and differentiated by color. That may bring out the competitive structure better.
Georgette has a nice post summarizing issues with picking colors when producing charts. Her blog is called Moved by Metrics.
Meanwhile, Martin finds a shockingly poor pie chart here.
There was a time where you'd find the kind of heatmaps featured here by Nathan as wallpaper in my office. It's a great visualization tool for exploring temporal patterns in large data sets. However, I'd never even think of putting these in a presentation. It's a starting point, not an end-point, of an analysis project. Some things are wonderful for consumption only in private!