This paper deals with various applications of conservation
laws on networks. In particular we consider the car traffic,
described by the Lighthill-Whitham-Richards model and by the
Aw-Rascle-Zhang model, the telecommunication case, by using the
model introduced by D'Apice-Manzo-Piccoli and, finally, the
case of a gas pipeline, modeled by the classical $p$-system.
For each of these models we present a review of some results about Riemann
and Cauchy problems in the case of a network, formed by a single vertex
with $n$ incoming and $m$ outgoing arcs.