Ever wondered how Australia's fertility rate compares to the rest of the world? You can track that -- along with dozens of other stats -- in a neat animated format on the OECD Factbook eXplorer site.
While the global comparison data used by the OECD is often used in other online reference sites like Wikipedia and Wolfram Alpha, the neat trick on the OECD site is the animated view of how a figure changes over time. Select a data set, click on a country, then hit the play button to watch the figures change. OK, it's a potentially serious time sink, but it's also a good tool to store in your reference site arsenal.