Programmable arbitrary precision RPN calculator. Zip file, download will start immediately.
http://public.planetmirror.com/pub/cug/vol_400/468_01.zip
X-Bc is desktop calculator that provides lots of functionality for scientific working. Input and output stay visble at all time for correction and comparation. It's a frontend to bc.
http://x-bc.sourceforge.net
mcalcdos is a free command line linear algebra calculator capable of matrix, vector and polynomial operations in real and complex fields.
http://www.angelfire.com/space/matrixcalc/
Small, open source (free), scientific and engineering, JavaScript-programmable calculators.
http://scal-2.sourceforge.net
DateCalculator v3.1.0 by Joesoft
http://www.joesoft.net/
Desktop printing calculator. Prints in columns and color on standard-sized paper.
http://www.angelfire.com/biz/ccsprog/Calculators.htm
2D and 3D graphing calculator for Linux with multiple graphing modes.
http://fung-calc.sourceforge.net
Covers diverse topics such as algebra structure, names for large numbers, how to compute pi and games.
http://db.uwaterloo.ca/~alopez-o/math-faq/