Areas and volumes
Animations
Animations: Generating the cross-sections of a pyramid. [David Hill]
Animations: Approximating the volume of a pyramid by cross-sections. [David Hill]
Animations: Generating the cross-sections of a horn-o-plenty. [David Hill]
Animations: Approximating the volume of the horn-o-plenty by cross-sections. [David Hill]
Animations: Generating the cross-sections of a pyramid over an equilateral triangle. [David Hill]
Animations: Approximating the volume of this pyramid by cross-sections. [David Hill]
Animations: Generating the cross-sections of a sharp "pup tent." [David Hill]
Animations: Approximating the volume of this pup tent by cross-sections. [David Hill]
Applets
Archimedes and the computation of pi: Use both inscribed and circumscribed polygons to calculate the area of a circle and get numerical estimates for pi. [Peter Alfed]
Volume of a solid: See the cross-sections and the solid approximations in determining the volume of a circular wedge. [IES]
Volume of a solid: See the cross-sections and the solid approximations in determining the volume of a solid which looks a lot like Frank Gehry's Winton Guest House. [IES]
Calculating simple volumes: A tutorial with nice applets showing approximations by disks. [University of British Columbia]
Volume of a solid of revolution (1): An applet which shows a parabola revolved around the x-axis to form a parabolid; you can view it either as an object rotating or by looking at it's cross-sections. [IES]
Volumes of solids of revolution: A nice applet showing successive approximations by disks. Also has links to some practice problems. [Dartmouth]
Solids of revolution: Plots the given solid of revolution. [Vanderbilt toolbox]
Online problems
Problems: Areas between curves. Includes graphs and solutions. [Visual calculus]
Problems: Volumes of solids by cross-sections. Includes graphs and solutions. [Visual calculus]
Problems: Volumes of solids by cylindrical shells. Includes graphs and solutions. [Visual calculus]