In Australia,
Data.gov.au provides an easy way to find, access and reuse public data. "Our team works across governments to publish data and continue to improve functionality based on user feedback. We encourage you to use government data to analyse, mashup and develop tools and applications to benefit all Australians. Geospatial datasets on data.gov.au and from other spatial indexes are now available through the National Map."
The National Map is a powerful interactive mapping system, through which you can view and combine many sources of mapping data, both at a national and local level, and share the resulting mashup on the web. You can even add your own data (eg as a spreadsheet, GeoJSON or KML file).