I am working on building out park data for my web site. My site is about hiking, so I want to get a list of parks and cities in the world.
Is that possible? Where can I get/download/see such unified information?
Geonames provides populated places and park information, and includes both an API and data downloads. This is based on a historical set of global data curated by the US government, but since supplemented by volunteered geographic information.
Natural Earth provides populated places and national parks within the US in shapefile format.
Open Street Map
Recreational (Local) Parks http://wiki.openstreetmap.org/wiki/Tag:leisure%3Dpark
US National Parks http://wiki.openstreetmap.org/wiki/US_National_Park_Service_Data
source is http://www.nps.gov/gis/data_info/
OpenStreetMap (OSM) advantages are it is a free wiki map (including commercial entities can use it for free). Limitation is that data coverage in rural areas can be very limited.