The Political Arithmetik blog has great graphics pertaining to, surprise surprise, political matters. I really like the ones portraying Presidential approval ratings.
This chart plots all the different polls (grey dots) at once; the blue line is the estimated approval rate over time while the scatter of grey dots provides an estimate of the reliability of the blue line.
Different polls are different random samples of the population. Random sampling is not fool-proof; any one sample has a chance, albeit small, to poorly represent the population. That's why the dots add greatly to the chart.
Derek pointed me to a different chart, a simple dot plot that shows Bush's 2006 mid-term approval rate was the 2nd worst since 1946. To paraphrase him, this is a scenario in which the chart does not add much because the underlying data is a simple ranked list.
He also suggested differentiating the 2nd term presidents from the one-termers.
Shown below is another view of the data, emphasizing the time dimension. The linked dots represent two-term presidents. The gridlines delineate the minimum, average and maximum approval ratings over time. Another line shows Bush's 2006 approval rating, which is the 2nd worst since 1946.
Lots of other great charts at this blog. Check them out.