Things I'd like to add.  Assuming these are actually possible.

%_smp_ncpus_max for EL5

python2 macros for EL6 and EL5

%__global_ldflags in EL6 (and maybe EL5)
  Requires redefinition of %cmake, %cmake_kde4, %qmake_qt4 and %configure

%make_build for EL6 and EL5