We expect that data parallel versions of Fortran will eventually be able to efficiently support a large fraction of large science and engineering simulations. However, more general and less demanding on the compiler, are extensions of Fortran which allow the user to explicitly generate the messages needed on MIMD machines. The resultant ``Fortran plus message passing model'' (Fortran + MP), is suitable for all problems for which Fortran is a reasonable language on a conventional computer. Fortran + MP is usually more time consuming for the user to develop than data parallel Fortran, and is only suitable for MIMD machines. However, in this broad class (MIMD) of distributed or shared memory machines, Fortran + MP is portable and scalable using such message passing systems as PVM and the new industray standard MPI (Message Passing Interface). Some metacomputing and, in particular, use of novel World Wide Web technology is driving much interesting work in this area.