What types of atomic orbitals of the central atom mix to form hybrid
orbitals in PF5 and SO3^2-?

The atomic orbitals of the P atom form sp3d hybrid orbitals in PF5. 
PF5 actually has two possible structures:  trigonal bipyramidal, in
which there are three F atoms equally spaced in a plane around the
"equator" of the P atom, and two additional F atoms "above" and
"below" the P.  To first order, equatorial bonds are formed from sp2
hybrid orbitals of the P atom, and the axial bonds are formed from pd
hybrids, in which the d(z^2) atomic orbital is used.  The equatorial
and axial bonds are therefore not equivalent.

In SO3^2-, the atomic orbitals of the S atom hybridize to form sp3
orbitals, three of which are bonded to oxygen atoms, and the fourth
contains a lone pair of electrons.

See: 

http://www.byui.edu/ricks/employee/MANNERL/Chemistry%20105/Molecular%20Structure%20and%20Covalent%20Bonding%20Theories_8.ppt

http://www.unb.ca/courses/chem2222/Tuesday%20Jan%2029%20B&W.ppt

http://faculty.plattsburgh.edu/gerald.kokoszka/che430/vsepr_and_hybrid_orbitals.htm