From: http://crd.lbl.gov/~osni/marques.html#BLZPACK

BLZPACK (for Block LancZos PACKage, release 04/00) is a standard Fortran 77 implementation of the block Lanczos algorithm intended for the solution of the standard eigenvalue problem Ax=µx or the generalized eigenvalue problem Ax=µBx, where A and B are real, sparse symmetric matrices, µ an eigenvalue and x an eigenvector. The development of this eigensolver was motivated by the need to solve large, sparse, generalized problems from free vibration analyses in structural engineering. Several upgrades were performed afterwards aiming at the solution of eigenvalues problems from a wider range of applications. 

Documentation: user's guide, technical report and comprehensive bibliography.

Source code: blzpack.tgz, blzpack.zip.