ggmap

ggmap makes it easy to retrieve raster map tiles from popular online mapping services like google maps, open street maps, cloudmade and stamen:

library(ggmap)

ggmap(get_googlemap())
ggmap(get_stamenmap())
ggmap(get_stamenmap(maptype = "toner-background"))

Use qmplot() in the same way you'd use qplot(), but with a map automatically added in the background:

downtown <- subset(crime,
  -95.39681 <= lon & lon <= -95.34188 &
   29.73631 <= lat & lat <=  29.78400
)

qmplot(lon, lat, data = downtown, maptype = "toner-background", color = I("red"))
qmplot(lon, lat, data = downtown, maptype = "toner-lite", geom = "density2d", color = I("red"))

Installation