On the Internet a mashup is the marriage of data and some sort of visualization, typically a map.
DataMasher is relatively new site that collects data produced by the federal government (much of it pulled from
Data.gov) and makes it available as a downloadable spreadsheet or interactive map. Typically these data sets are broken down by state, so you can click on a state to see individual state data or look at state rankings in a table. DataMasher currently hosts 375 mashups, which cover the gamut of topics: health, economy, environment, crime, transportation, etc. You can browse these by "the latest," "highest rated" and "most discussed". Right this moment, the mosted discussed mashup is "
Hate Crimes vs Population" (California is 15th).
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More at DataMasher.Org