Herwig++ 2.1 release note.

A new release of the Monte Carlo program Herwig++ (version 2.1) is now available. This version includes a number of significant improvements including: an eikonal multiple parton-parton scattering model of the underlying event; the inclusion of Beyond the Standard Model (BSM) physics; and a new hadronic decay model tuned to LEP data. This version of the program is now fully ready for the simulation of events in hadron-hadron collisions