MIME Object Security Services. It's a technically superior alternative to PGP, but one with an uncertain future. It's not being actively developed by anyone other than TIS, and their TISMOSS prototype implementation is far from being generally usable.
What do you mean by "technically superior"? What technical merits does MOSS have over PGP? It does have a better protocol with which to integrate it into mailers, but it is only a transmission protocol, not a security mechanism change. Worse, MOSS uses X.509, which requires a lot of overhead for certificates. On the other hand, the MIME-PGP protocol can provide the same integration functionality as MOSS and still allow the use of the simple PGP certification structure that already exists. -derek