InstaCalc
Kalid Azad sent me an email about his online calculator site called InstaCalc and it is really impressive. It's the kind of project that people have talked about for years - one can type equations into the program and it just calculates the results. You can enter something like 5% X 100 and get 20 as your answer. Or mix Hex, Binary, Octal and Decimal in the same formula - 0x1a + 0b1001 +0o10 - 1 and get 42.
You can save and share your mini-programs with others as well. There are a number of saved calculations there already. Try out this sample saved calculation page that demonstrates hex, octal and binary calculations. Or this one on doing a home loan calculation.
I can see this being useful in a lot of ways - getting an understanding of variables and different number systems being only the most obvious.
