Projections appropriate for global analysis that preserve area and that preserve distance (but not necessarily in the same projection)

The latest PostGIS has a "Geography" data type which does calculations on Lat/Lon WGS84 spatial reference system data, and returns the distance or area results in meters/sq. meters based on the WGS84 ellipsoid. So you could bring your country data into PostGIS in WGS84 Lat/Lon, using Geography instead of Geometry and then create the buffers, and do the area calculations with the built in functions.

See: ST_Buffers ST_Area and PostGIS Geography

-- Micha

Map projection selection tool suggests Eckert IV and Mollweide http://people.oregonstate.edu/~savricb/selectiontool/

EDIT: This link above is dead, but the tool seems to have moved to here: http://projectionwizard.org