  From Dalitz-plot analyses of $D^+\to\pi^-\pi^+\pi^+$ and $D^+\to
K^-\pi^+\pi^+$ decays, we find evidence for light and broad scalar resonances
sigma(500) and kappa(800). From a Dalitz-plot analysis of
$D^+_s\to\pi^-\pi^+\pi^+$ decays, we measure the masses and decay widths of the
scalar resonances f_0(980) and f_0(1370).
