Source: http://lifehacker.com/5939276/findthedata-compares-tons-of-data-side+by+side-is-a-research-gold-mine
FindTheData is part of the FindTheBest family of comparison sites. While FindTheBest compares dozens of categories to help you make better decisions (e.g., pick the best college), FindTheData is more of a research/reference tool.
Once you browse to or find the datapoint you want to compare (e.g., libraries, hurricanes, or serial killers), you can filter the search results, select individual items to compare side-by-side, and see more in-depth details.
Fair warning: It might be hard to stop browsing the databases, especially if you're a trivia buff.