The Forth Scientific Library is included in
Some of the FSL routines have been ported to Krishna Myneni's kForth,
which does not have a separate floating-point stack.
Work on improved testing of FSL files can be found at this location.
A (not completely up-to-date) version of the FSL is included in Andreas Kochenburger's MinForth.
David N. Williams has a collection of complex number implementations and tests.
Links from that page lead to other material related to Forth numerical programming.
An archive copy of Julian Noble's web pages from his courses in Computational Physics at the University of Virginia is located here.
Included is a variety of forth-related material.