[dsr_]

If you have an Android device, HandyCalc is free-beer and very, very good.

If you need serious calculating, there are all sorts of open source packages for Linux, and a number of devices of varying capabilities to run it on.

[xymostech]

I actually think the problem with all of these solutions is standardized testing. Throughout high school, I used my iPhone as a calculator for everything, but whenever we needed one for a test I had to drag out my old TI, because people were afraid I would cheat if I had internet access.