Appshopper Link This is a very good calculator that I used in epidemiology and biostatistics. It has a number of mode, and for me the thing I love is the ability to use RPN (Reverse Polish Notation like HP calculators). The devs keep in updated, and tweak some bugs occasionally. May be far too much calculator for some people, but if you want / need scientific calculations / graphs, formulas, etc. you might want to consider this one...
