gdcalc
financial, statistics, scientific and programmers calculator
... are probably familiar with algebraic calculators. Very briefly, while simpler and more natural to use, RPN calculators need some study eg. they have an Enter key instead of the equals key.
New home page: http://bhepple.com/doku/doku.php?id=dcalcunix
Old home page: http://bhepple.freeshell.org/dcalc/unix