  We report on the observation of two Feshbach resonances in collisions between
ultracold $^6$Li and $^{87}$Rb atoms in their respective hyperfine ground
states $|F,m_F>=|1/2,1/2>$ and $|1,1>$. The resonances show up as trap losses
for the $^6$Li cloud induced by inelastic Li-Rb-Rb three-body collisions. The
magnetic field values where they occur represent important benchmarks for an
accurate determination of the interspecies interaction potentials. A broad
Feshbach resonance located at 1066.92 G opens interesting prospects for the
creation of ultracold heteronuclear molecules. We furthermore observe a strong
enhancement of the narrow p-wave Feshbach resonance in collisions of $^6$Li
atoms at 158.55 G in the presence of a dense $^{87}$Rb cloud. The effect of the
$^{87}$Rb cloud is to introduce Li-Li-Rb three-body collisions occurring at a
higher rate than Li-Li-Li collisions.
