  Version 2.0 of CRPropa is public software to model the extra-galactic
propagation of ultra-high energy nuclei of atomic number Z<26 through
structured magnetic fields and ambient photon backgrounds taking into account
all relevant particle interactions. CRPropa covers the energy range 6*10^16 <
E/eV < A*10^22 where A is the nuclear mass number. CRPropa can also be used to
track secondary \gamma-rays and neutrinos which allows the study of their link
with the charged primary nuclei -- the so called multi-messenger connection.
After a general introduction we present several sample applications of current
interest concerning the physics of extragalactic ultra-high energy radiation.
