Listings are generally in alphabetical order. Comments in quotes are from manufacturers' sites or from members. The appearance of any link here does not imply JRA endorsement.

OpenCPN  is a free software project to create navigation software for use under way or as a planning tool.  OpenCPN is developed by a team of active sailors using real world conditions for program testing and refinement. It is fully cross-platform and can be used on Linux, Mac and Windows.

You can purchase QCad Professional (recommended) and the QCad book at: RibbonSoft, GmbH.  If you use Linux you can install the GPL version from your distros package manager. It is not as full featured as Qcad Prof, but for reading .dxf files and light CAD work it's OK.

You can get the Designfoil foil analysis program, with an easy-to-use graphical interface, from http://www.dreesecode.com/ . Use it to study the aerodynamics of sail cross-sections and planforms. The demo version is free and can be used for an unlimited time, but is limited in some aspects of storing and exporting your work. This is Windows only but it does work under wine for Linux users and of course can be run in a virtual machine or PC emulator.

David Tyler found a spreadsheet version of the STIX calculation on http://www.boatdesign.net/forums/stability/sailing-boats-stability-stix-old-ratios-13569.html He says you will read in https://app.box.com/s/x07nbtk3g1x9v8kvr4cr that STIX is a useful, but not foolproof tool for analysing boat design.