We report total cross sections (TCS) measurements for positron scattering on N2, Ar, He and three cyclic hydrocarbons. The data have been obtained with a new linear low-energy spectrometer at Trento University. Both nitrogen and argon total cross sections shows a flat part in TCS from few eV up to the positronium formation thresholds. For cyclocarbons he has found very high values of the TCS in low energy range. Modeling using effective range theory is performed for benzene and cyclohexane. In He results we found some resonant structures indicating formation of virtual positronium.