In this thesis I have investigated the electronic structure of two-dimensional electron liquids (2DEL) induced at different surfaces of the transition metal oxide band insulators SrTiO3, KTaO3 and anatase TiO2 by angle-resolved photoemission spectroscopy (ARPES). I present high-resolution ARPES data, spin-resolved ARPES data and the results of self-consistent tight binding supercell calculations of 2DEL band structures.