[R] Drawing maps in R?

[Spencer Graves]

      What tools and documentation exist for producing maps and working 
with polygon and polylist objects in R beyond the following: 

      * Packages maps, mapproj, maptools, and mapdata. 

      * Becker and Wilks (1993, 1995), listed as references in the 
documentation on the "map" function. 

      Thanks,
      Spencer Graves