Geomview - Interactive 3D viewing program for Unix. Free under GPL.
The Kenzo Program - A computer program for computational algebraic topology.
Liverpool University Knot Theory Group Programs and Procedures - Four programs, each calculating some invariant from a closed braid presentation. Free to download. Pascal.
MING - Computes the MD energy of a polygonal knot. Available via ftp.
OPTi - Macintosh freeware which visualizes quasi-conformal deformations of the once-punctured-torus groups. It interactively draws the isometric circles, the Ford region, and the limit set.
Simplicial Homology - A proposed GAP share package. May be tried online.
SNAP - Exact computation of hyperbolic 3-manifolds and their arithmetic invariants. Written by O. Goodman in an ARC-funded project of Hodgson and Neumann.
SnapPea - A program for creating and studying hyperbolic 3-manifolds. Free source available in C.
SnapPea PC - SnapPea for Windows 95/98/NT by A.C. Manoharan.