  Although the primary goal of ESA's Planck mission is to produce high
resolution maps of the temperature and polarization anisotropies of the Cosmic
Microwave Background (CMB), its high-sensitivity all-sky surveys of
extragalactic sources at 9 frequencies in the range 30--860 GHz will constitute
a major aspect of its science products. In particular, Planck surveys will
provide key information on several highly interesting radio source populations,
such as Flat Spectrum Radio Quasars, BL Lac objects, and, especially, extreme
GHz Peaked Spectrum sources, thought to correspond to the very earliest phases
of the evolution of radio sources. Above 100 GHz, Planck will provide the first
all-sky surveys, that are expected to supply rich samples of highly
gravitationally amplified dusty proto-galaxies and large samples of candidate
proto-clusters at z~2-3, thus shedding light on the evolution of large scale
structure across the cosmic epoch when dark energy should start dominating the
cosmic dynamics.
