The best replacement for lapack is blas.

The best alternatives to lapack are rated as following:
★★★★★  blas
★★★  linpack
★★★  eigen
★★★  gsl
★★  lapack
★★  mkl
★  arpack
★  scalapack

Your alternative for lapack is not listed? Suggest!
Speaking about lapack, one probably shouldn't forget about atlas.

Other search terms related to lapack and their ratings are:
★★★★★ atlas
You have in mind a companion for lapack and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of lapack in all years. Click on graph for more.
lapack
blas
linpack