A website that does a really good job at collecting APIs in Sweden is Mashup.se, it’s being run by Andreas Krohn who is hosting the event Nordic API conference later this year. Apparently, the most popular services being used revolves around phone number lookups, government financial services and weather information.
Top three most viewed APIs
PTS sök operatör API (phone operator lookup)
With this API you can lookup which operator a phone number belongs to
GovData API (Government Data)
List all the companies that sells their services to the government and what departments spend their money on.
Temperatur.nu API (temperature service)
This API helps you get the temperature for a specific location.