Data Desk (hosted)
A tool for Exploratory Data Analysis (EDA). It is one of the oldest Macintosh programs still actively developed and sold (for OS X and Windows). A version for Macintosh 680x0 is freeware.
My favorite program for simple calculations.
"General purpose graphing scientific calculator."
"For graphing, and otherwise exploring, mathematical relationships."
"Full-featured replacement for Apple's standard Calculator DA.
Calculator with hot key activation.
Extended Calculator (hosted)
Four calculators in one program.
"Scientific plotting and statistics".
A "plotting application".
Linear Regression Pro (hosted)
Linear Regression for one Y and one X.
"Writes outlines of proofs in elementary set theory".