These are freely available datasets from here and around the world. Some are accessible via API's, which are an automated way to mine data into software like Google Refine.
Data.gov.au -  Is hosted by the Australian Government. At present it contains over 1000 datasets, including datasets on Construction materials, housing finance, planning, Property, and Transport. Contains a bunch of interesting apps and links to GIS software also.
Datacatalogs.org  - Is a portal to open Datasets from around the world. API compatible.
Eurostat  - Business and demographic statistics from the Eurozone. Also contains specialist datasets like rural development and land cover/use.
Statista  - A wonderful data portal with an easy to use search interface. Contains a wealth of economic data including construction data from around the globe.
World Bank Data Catalog  - A wealth of datasets from all parts of the globe. Contains World Development Indicators, Environmental stats, population forecasts, Global Development Indicators and much much more! Largely API compatible