Recommended on a couple of Business Library blogs – http://piersonrevesz.wordpress.com/2013/02/01/quandl/ and researchfinancial above.
Quandl is a new portal that has indexed millions of numerical datasets on the Internet. More information on the background and features is available through their FAQ pages. When you click on a particular dataset listed in the Quandl index, Quandl goes to the original source of that data, extracts the most recent version of that data, cleans it up, and gives it to you in the format of your choice.
Specific topic pages were created on Markets, Economics, Demography & Society.
A big thank you goes to Prof. dr. André Lucas who pointed out the Quandl portal to me.