http://www2.epa.gov/sunwise/uv-index Includes a lot of UV data
Such as maps of UV average for each month
http://www.arpansa.gov.au/uvindex/models/ausuvmodels.htm Australia
http://www.who.int/uv/resources/link/indexlinks/en/ WHO has links to many places around the globe
WHO table of UV index in major cities vs month of the year
http://www.accuweather.com/en/world-weather?p=accuweather Accuweather has daily UV maps
See also VitaminDWiki