vCalc is the other side project I have going on right now. It's a simple RPN style calculator written for Win32. Underlying vCalc is a Scheme interpreter that I talk about a little here. The ultimate goal for vCalc is to have a calculator that can be easily extended with Scheme functions, in addition to the keystroke sequences you might expect. As it turns out, there are a lot of interesting problems that crop up trying to make this work right. I hope to blog more on this in the future.
Like Noisemaker, vCalc is shareware available through IceGiant.