[R] us zipcode data map

[Mike R]

i've search the email archives, searched the documention 
of various map packages and done an R-site search, but 
have been unable to find direct resources for creating maps 
of the US that are colored or annotated or ... by zipcode 
data.  

For example, create a map of the US and color each zipcode 
region by its population using two vectors z,p containing the 
zipcode and population, respectively.  I'm not looking for data 
to fill z, and p.  I'm looking for some highend functions to 
display on a map the data that I already have.

Cheers,
Mike