Very reliable computational tools are presently available for the ab initio quantum-mechanical treatment of crystalline systems. In order to exploit translational periodicity, they adopt as a rule one-electron Hamiltonians, either based on density functional theory (DFT), or on the Hartree-Fock (HF) equations as a zero-level approximation for the solution of the Schrodinger equation. As concerns the former approach, it is almost straightforward to implement DFT at the same level of accuracy in crystalline as in molecular applications. On the contrary, the problem is still open of how to go beyond the HF approximation in the case of periodic systems, while a variety of powerful post-HF schemes have been developed and are currently used in the field of molecular quantum chemistry. A way out of this difficulty could now be offered by the implementation of efficient techniques of localization of the HF manifold of crystals. We describe here briefly one of such techniques which has recently been developed to generate well-localized Wannier functions (WF) for non-metallic periodic structures, starting from canonical crystalline orbitals in an atomic orbital representation. WFs are next shown to be ideally suited for transferring to the periodic case the local-correlation methods developed by Pulay, Werner et al. for molecules. Finally, it is proposed to use WFs for formulating new embedding schemes which could allow both the HF and the post-HF solution of the problem of local defects in crystals to be obtained in a simpler way than presently possible.