  Based on the ladder dual-fermion approach, we present a comprehensive study
of the phases of the isotropic Hubbard model on the triangular lattice. We find
a rich phase diagram containing most of the phases that have already been
experimentally observed in systems where the interplay between geometric
frustration and electronic correlations is important: paramagnetic metal,
paramagnetic insulator, Mott-insulator with $120^{\circ}$ antiferromagnetic and
a non-magnetic insulating state, i.e. possibly a spin liquid state. This
establishes that the Hubbard model on frustrated lattices can serve as a
minimal model to address the intricate interplay of frustration and
correlation. We also show that entropic considerations can be successfully used
for understanding many striking features of the triangular systems, such as the
large thermopower found in Na$_{x}$CoO$_{2}\cdot$$y$H$_{2}$O.
