Over the past few months I've become increasingly fond of Edward Tufte's Slopegraphs for data visualization. They aren't just good for comparing across time, but also across two categories.
The NHL playoffs are underway and so some visual analytics are in order. Have a look at the relationship between payroll and Stanley Cups.
Recently a small data set was posted on a discussion board I read. 5 columns by 15 rows. This small bit of data yielded an immense number of opinions and visualizations.