Esri has launched ArcGIS Open Data as a portal for users to search, download, and visualize open data:
Since July 2014, more than 1,200 organizations from all levels of government, including the National Geospatial-Intelligence Agency (NGA), and the cities of Raleigh, North Carolina; Tampa, Florida; Charlotte, North Carolina; and Muroran, Japan, have used Esri’s ArcGIS Open Data to configure custom open data sites to serve local citizens and businesses. Now the public can search across all these sites to find authoritative data by location and topic.
Currently, more than 1,480 organizations have contributed over 23,000 open GIS data sets. Users can search by data topic (e.g. streets or parks) and by location. A browsable list of data options is linked to the map above the search results. Hover over a search result to see where the geographic boundary is on the map (only works for the first few results since scrolling down moves the map out of the screen view). Click on a result link to see the metadata and attribute information. The download button next to each result allows the user to download the GIS data as a spreadsheet, KML file, shapefile, or the link to the GeoJSON or GeoService API. Datasets can also be filtered before being downloaded. No registration seems to be required to search or download GIS data.
Visit: ArcGIS Open Data