fortran??!

[Stephen Judd]

I need a Fortran compiler to set up a package I want to install.
I have looked all over the net for one. I've especially looked
all over gnu.org, and nowhere does it say where or how to
download one. There are amazingly complete documents
about Fortran (e.g. http://gcc.gnu.org/onlinedocs/gcc-4.0.2/gfortran/)
but it all omits the crucial detail of where to get it!!
I suspect I am missing something really stupid.

BTW, I have gcc and g++ etc installed, but no g77 or f77 etc.