Most useful thing learned in Calc

[Dan Zollman]

Well, I can't think of anything at the moment...I think I learned something...

but here's something interesting:
The solid created by the graph of 1/x rotated around the x-axis has finite volume but infinite surface area. As my math teacher said, you can fill it with paint, but you can never paint its surface. This "paradox" is known as Gabriel's Horn.

[Tom Bottiglieri]

I like calc. If nothing else, its a great step into higher level problem solving.

As for individual concepts.. I feel I benefited from all of the vector stuff, as well as integration and differentiation concepts for signal processing.