Creating shaded zip code maps (newbie)

[Steve Gertz]

All,

This is my first time dipping my toe into the GIS world, after a couple
of years of working on problems that dealt with geography.  I'm finally
getting the chance to visualize our data.

I'm tring to create a highlighted view zip codes, based on the number of
ad impressions we have for each zip code.  I'd want to do some number
crunching and shade each zip code (or other geographical shape) between
white and some solid (with gray for no data).

I've got the 5 digit Zip code tablulation areas from the census.  From
there things get more tricky.  I think I want a raster image for each
scale of the map, but I can't find any interfaces that allow making the
raster files easy in perl.  I can't seem to find anything that will link
the raster and geographic data together.

Does anyone have advice for solving this type of problem?  Seems this
would be a great FAQ to add to the mapserver / gdal / grass / et al
websites.

Thanks in advance,
Steve