At low and high frequencies the microwave sky anisotropies include significant diffuse foregrounds emanating from our own Galaxy. At low frequencies there is synchrotron emission arising from high-energy cosmic rays spiraling in the Galactic magnetic field and thus radiating as well as free-free emission (or Bremsstrahlung) arising from collisions of electrons off each other and with ions. The synchrotron emission is highly polarized because the magnetic field defines a linear polarization whereas the free-free emission is unpolarized. At higher frequencies dust dominates the microwave sky anisotropy. This thermal dust emission is partially polarized due to the alignment of the dust grains by the Galactic magnetic field. A detailed account of possible dust alignment mechanisms is given. We also discuss the so-called Anomalous Microwave Emission (AME) at low frequencies, which could be due to electric dipole emission of extremely rapidly spinning small dust grains or possibly magnetic dipole emission. Line emission from CO and other small molecules is also discussed.