Quandl is a repository for datasets on the internet, it's free, open and very easy to use.
It collects more than 8,000,000 financial, economics and social datasets that you can search by keywords or browse by country, subject or source.
It's possible to visualize, download (excel, csv, json, xml), save, share, combine with other datasets to create a superset.
You can also search dayasets in Quandl using API.
Here you can find the complete list of all Quanldl sources with their direct links and the description of statistics included.
For more information visit the "About" page of Quandl.