We report strong variations in the Raman spectra for different single-layer graphene samples obtained by micromechanical cleavage. This reveals the presence of excess charges, even in the absence of intentional doping. Doping concentrations up to $\sim {10}^{13}{\mathrm{cm}}^{-2}$ are estimated from the $G$ peak shift and width and the variation of both position and relative intensity of the second order 2D peak. Asymmetric $G$ peaks indicate charge inhomogeneity on a scale of less than $1\mu \mathrm{m}$ .

We report phonon renormalization in bilayer graphene as a function of doping. The Raman $G$ peak stiffens and sharpens for both electron and hole doping as a result of the nonadiabatic Kohn anomaly at the $\Gamma$ point. The bilayer has two conduction and valence subbands, with splitting dependent on the interlayer coupling. This gives a change of slope in the variation of $G$ peak position with doping which allows a direct measurement of the interlayer coupling strength.