  The production of pseudo scalar, Eeta, Eta-prime, and vector, Omega, Rho,
Phi, mesons in NN collisions at threshold-near energies is analyzed within a
covariant effective meson-nucleon theory. It is shown that a good description
of cross sections and angular distributions, for vector meson production, can
be accomplished by considering meson and nucleon currents only, while for
pseudo scalar production an inclusion of nucleon resonances is needed. The
di-electron production from subsequent Dalitz decay of the produced mesons,
$\eta'\to \gamma \gamma^* \to\gamma e^+e^-$ and $\omega\to \pi\gamma^*\to \pi
e^+e^-$ is also considered and numerical results are presented for intermediate
energies and kinematics of possible experiments with HADES, CLAS and KEK-PS.
  We argue that the transition form factor $\omega\to \gamma^*\pi$ as well as
$\eta'\to \gamma^*\gamma$ can be defined in a fairly model independent way and
the feasibility of an experimental access to transition form factors is
discussed.
