Arclength and surface area
Animations
Animation: A look at Gabriel's Horn. [Lane Vosbury]
Applets
Arc length and surface area: A tutorial which includes a nice applet showing how sums of line segments can be used to aprroximate arclength. Also contains some worked examples on arc length and surface area. [University of British Columbia]
Arc length of a curve: Computes the arclength of any function you give it. [Vanderbilt toolbox]
Surfaces of revolution: Plots any given surface of revolution. [Vanderbilt toolbox]