TOMS450 is a FORTRAN77 library which implements ACM TOMS algorithm 450, for seeking the minimizer of a scalar function of N variables.
The text of the algorithm as printed in the original reference had a number of errors which were corrected in a remark made the following year. The text of the algorithm has been corrected accordingly.
The text of many ACM TOMS algorithms is available online through ACM: http://www.acm.org/pubs/calgo or NETLIB: http://www.netlib.org/toms/index.html.
TOMS450 is available in a FORTRAN77 version.
MINPACK, a FORTRAN90 library which contains routines which can minimize the absolute value of a function of several variables.
TEST_OPT, a FORTRAN90 library which contains routines defining a number of scalar functions of multiple variables to test minimization routines.
You can go up one level to the FORTRAN77 source codes.