I'm teaching reaction equilibrium next week, and most of my students have a lot of trouble with the quadratic formula, so I figured I'd download a calculator. Oddly enough, I didn't find a quick (and small, for PDAs) excell-based calculator, so I wrote one.
If you ever need to calculate roots of quadratic polynomials, feel free to steal it:
Download my quadratic solver at lemonizer.com
BTW: I did find a web-based one here
also, if you want to modify it or integrate it...the password is...oh figure it out...or email me