This wiki begins to explore the existence of countrywide data portals around the world.

Lists of Open Data Portals

DataCatalogs.org: a website aiming to be the most comprehensive list of open data catalogs in the world. It is curated by a group of leading open data experts from around the world
Open Data Hubs Worldwide - Buzzdata
Open ! Government Data - Open Knowledge Foundation (spreadsheets that contain different sheets giving information about open government data catalogues from around the world
Public Sector Dataset Catalogs - CTIC
Open Data Initiatives - Civic Commons
World Government Data - The Guardian
Government Data Catalogs - Sunlight Labs
Open Data Sites - Data.gov
Also of note, city-wide data sites from GovLoop

International Data Portals - OpenCongress Wiki