Mapping Blues: Where is the Data?
While you can buy data, there is so much public data out there to check out first. Resources for data can be broadly applicable, or very specific for narrow uses. Here are some resources I have found useful for finding data, often for free, to use in my mapping projects:
U.S Census: Yes, most everything that the government collects in those giant census surveys is available to download. Tons of demographic information, boundary files for outlining states, counties and cities, and many other resources for free.
Data360: Lots of great data sets, slideshows and graphs contributed by users. Its helpful to click through graphs and slideshows that are close to what you are looking to map to see how others approached the problem. As an occasional surfer, I find this contributed graph of shark attacks somewhat comforting.
UNdata: Tons of international data covering , demographic, health, trade, education information and more - a particularly good resource for international development organizations. The site provides multiple options for filtering data, showing/hiding columns, and for exporting to work in multiple mapping/GIS software.
Freebase: Another resource for data contributed by users. I find this site easy to navigate, and has some really interesting data. All contributed data can be associated with topics, grouped together by types, which in turn are grouped together by domain. This structure allows you to find, say, data on the topic Dick Cheney as well as on the type U.S. Vice President - providing various perspectives on related information.
Huge Data Lists: Not for the faint of heart, these are goldmines for finding public data resources, but you will have to dig. Check out the publicdata tag in delicious, or this giant list from Peter Skomoroch.
I would love to hear about your data and mapping projects, and where you found useful information for them.