OpalCalc v1.7 - Multi-line, notepad-like, update-as-you-type calculator
[OpalCalc has been updated from 1.0 to 1.7 - see my comment reply below for more details]
OpalCalc is a brand new type of calculator for the PC. As easy to use as Notepad or a word processor, OpalCalc allows natural language and multi-line support so you can go back and adjust your previous calculations. Download from:
http://www.skytopia.com/software/opalcalc/