We present a scenario for iron-pnictide superconductivity mediated by charge fluctuations that are strongly enhanced by Fe-As intersite electronic interactions. Deriving an eight-band extended Hubbard model including Fe 3d and As 4p orbitals for the LaOFeAs family, we show that charge fluctuations induced by p-d charge transfer and As orbital polarization interactions in the Fe-pnictogen structure peak at wavevectors (0, 0), and (π, 0) and (π, π) respectively. Intraorbital pairing attraction develops at these wavevectors and the solution of the linearized Eliashberg equation shows robust s-wave superconductivity with both S+ pm$ and S++ symmetry.