Here's an example I featured in my list of 7 Awesome Things about R (awesome thing #3: graphics and data visualization). The Learning R blog features a reproduction of a graphic that recently appeared on Flowing Data. It shows the colors in a box of Crayola crayons: before 1949 there were only 8, but over the years additional colors have been added to the mix. Today, there are 120 colors, and the chart below shows the progression of colors added over time.
The amazing thing about this graph isn't just that it's reproduced in R from a hand-crafted original. The amazing thing is that this chart is completely automated: it reads the list of colors from history directly from the list of Crayola colors on Wikipedia, creates barcharts for each time period, and sorts the colors in a pleasing manner (by converting them to the HSV color space) before exporting the custom chart to a PNG file. All of this is done in less than 30 lines of R code. If Crayola introduces a new set of colors this year, then as long a someone updates the Wikipedia page, a new, up-to-date version of this graph can be created in seconds. Now that's awesome.