John Little's DVS workshop on Mapping in R. Follow along in R markdown files. Uses the Tidyverse packages. Covers plotting coordinate points, map projections, thematic mapping with US Census and Bureau of Labor Statistics data, and the leaflet package. Includes links to the markdown files and sample data on GitHub.
Online interactive course from DataCamp. The first of four sections ("Basic mapping with ggplot2 and ggmap") is free. The others require payment ("Point and polygon data," "Raster data and color," and "Data import and projections").