Lecture Notes on CMB Theory: From Nucleosynthesis to Recombination
  These lecture notes comprise an informal but pedagogical introduction to the well established physics and phenomenology of the cosmic microwave background (CMB) between big bang nucleosynthesis and recombination. The dominant properties of the spectrum, temperature anisotropy and polarization anisotropy of the CMB all arise from this period. We review the physical processes involved and show how they are related to the observed phenomenology. 
Wayne Hu (KICP, U. Chicago)