  We study the spinless and spinful extended Hubbard models with repulsive
interactions on the kagome and the decorated honeycomb ("star") lattice. Using
Hartree-Fock mean-field theory, we show that interaction-driven insulating
phases with non-trivial topological invariants (Chern number or $Z_2$
invariant) exist for an experimentally reasonable range of parameters. These
phases occur at filling fractions which involve either Dirac points or
quadratic band crossing points in the non-interacting limit. We present
comprehensive mean-field phase diagrams for these lattices and discuss the
competition between topologically non-trivial phases and numerous other ordered
states, including various charge, spin, and bond orderings. Our results suggest
that $Z_2$ topological insulators should be found in a number of systems with
either little or no intrinsic spin-orbit coupling.
