It often takes so much effort to gather data in the first place that we rarely take the time to put the data into a visual form. If we take the time to present information visually though, it can have a much greater impact on recognition, retention and comprehension.
I've written about Communication Illusions and where optical illusions can mislead.
Michael Ogawa was inspired by this information visualization to create some stunning video's called code swarm that incorporate music, time, and statistics for the interactions that developers have on open source projects.
If your inclined to create your own charts and don't have Excel or a chart rendering control or tool, there's Google charts.