Stuart writes: "M[n]M is software that
supports processing of national standard MARC MeSH subject authority records for use in medical library online public access catalogs. While designed for use with Innopac M[n]M can also be used to manage MARC MeSH in other OPACs. M[n]M is freely available under the GNU Public License. To download M[n]M or to read more, go to library.med.nyu.edu/mm" [1].
There's also a very informative paper describing M[n]M available here [2].
Links:
[1] http://library.med.nyu.edu/mm
[2] http://library.med.nyu.edu/mm/mmtext.html