SpeedCrunch is a fast and compact calculator thatis designed to be controlled using the keyboard. There is support for a few built-in functions (with an autocomplete feature) as well as variables. Read more hot
(shareware) CalcExp is a science calculator that supports more functions than the Windows calculator, and is also a unit/currency/color converter. It supports 5 locales for formatting numbers. Its skin can be changed.
JRPN is a pop-up 35-function virtual scientific calculator that uses the Reverse Polish Notation method for data entry. Unlike an algebraic calculator which has an "equals" button, a Reverse Polish Notation (RPN) calculator does not use an "equals" key.
a simple IPv4 subnetting calculator