spatial clusters

Dear all,

I try to use SKATER algorithm (from package spdep) to classify the
countries in clusters taking account of the geographical position and from
macroeconomic indicators.

How to create a shapefile including my data about some socio-demographic
indicators (7),  for about 30 countries around the world (to be read with
readShapePoly)? 

Would be useful to suggest some good introductory lectures in spatial
statistics (links or books).  

Thanks you for your help.
Dorina


PS. Roger, Georg,  thanks a lot for your suggestions.