  Using 22.7M BBbar events collected with the BABAR detector at SLAC, we
present preliminary measurements of the branching fractions for charmless
hadronic decays of B mesons into two-body, quasi two-body and three-body final
states with pions, kaons, and rho and a0 resonances. In the search for
exclusive $B^0 \to \pi^+\pi^-\pi^0$, we measure ${\cal B}(B^0 \to
\rho^{\pm}(770)\pi^{\mp})=(28.9\pm5.4\pm4.3) \times 10^{-6}$, together with the
relative asymmetry ${\cal A}_{\rm phys} = -0.04 \pm 0.18 \pm 0.02$. We also set
the upper limits on $B^0 \to \rho^0(770)\pi^0$, non-resonant $B^0 \to
\pi^+\pi^-\pi^0$, $B^0 \to a_0^{\pm}(\to \eta\pi^{\pm})\pi^{\mp}$ and $B^0 \to
K^0\bar K^0$.
