We discuss two experiments involving spin-polarized tunneling through molecules. In the first experiment, we study nickel tunnel junctions made using a self-assembled-monolayer of octanethiol as a molecular barrier. The devices exhibit significant magnetoresistance, demonstrating that low-energy electrons can traverse the molecular barrier while maintaining spin coherence. In the second experiment, we measure Kondo-assisted tunneling via a carbon-60 molecule in contact with ferromagnetic nickel electrodes. We find that the Kondo peak in the differential conductance is split, by an amount that decreases as the magnetic moments in the two electrodes are turned from parallel to antiparallel alignment. We observe large negative values of the junction magnetoresistance due to the presence of the Kondo effect. @Footnotetext@In collaboration with J. R. Petta, S. R. Slater, R. C. Bialczak, J. Martinek, J. E. Grose, L. A. K. Donev, P. L. McEuen, D. C. Ralph