f77/f2c
FTP from netlib.att.com in /netlib/f2c (sources and patches)
g77
FTP from sunsite.unc.edu in /pub/Linux/devel/fortran
ftnchek
FTP from sunsite.unc.edu in /pub/Linux/devel/fortran and tsx-11.mit.edu in /pub/linux/packages/fortran
fort77
FTP from sunsite.unc.edu in /pub/Linux/devel/fortran
Toolpack
FTP from sunsite.unc.edu in /pub/Linux/devel/fortran and tsx-11.mit.edu in /pub/linux/packages/fortran
slatec
http://netlib2.cs.utk.edu
PGPLOT
http://astro.caltech.edu/~tjp/pgplot and FTP from astro.caltech.edu in /pub/pgplot
SciLab
FTP from ftp.inria.fr in /INRIA/Projects/Meta/Scilab

(Older versions of SciLab and PGPLOT can be found on sunsite.)