Are you looking for examples of big (or small) real world datasets to play with in Tableau?
I have pulled together the best free resources the web has to offer, below…
European Union Open Data Portal
A collection of data sets from the EU institutions.
Data sets from UK Governmental Agencies.
Various data sets including census and business microdata.
Data sets from the Greater London Authority.
Data management platform from the Open Knowledge Foundation.
World wide development and finance indices.
Public Data on Google.
Favourite subreddit for data.