Browser download:

ftp://ftp.mcs.anl.gov/pub/petsc/software_old/v2.1.6.petsc.tar.gz
	    

Unpack:

gunzip -c v2.1.6.petsc.tar.gz | tar xvf -
	    

creates the directory petsc-x.x.x where x.x.x is the PETSc version.