MacResearch.org uncovered a very capable and apparently overlooked scientific calculator, the Magic Number Machine.
The scientific calculator is notable for its expression history in a slide out drawer and 25 digits of precision.
Magic Number Machine
"Some people donit like calculators that emulate physical calculators (I generally donit like them either), but this is a really nice scientific calculator with support for complex numbers, different number bases, Matrix methods like Gaussian elimination, etc. It is also open source (and comes with an Xcode project, last time I checked)," the article said.
The Magic Number Machine requires Mac OS X 10.4, is a Universal Application and is free.