"integral" is referenced in the pages listed below.

Calculus: What happens if one of the limits of integration for a definite integral is infinity? Does the integral have a value? Or, what if the value of the integrand goes to infinity at one of the limits? This page describes how treat these cases as a use of limits. Interactive calculus applet.
The definite integral, the limit of a Riemann sum, can be interpreted as the area under a curve. This page explores some properties of definite integrals which can be useful in computing the value of an integral. Interactive calculus applet.
In calculus, a Riemann sum is a method for approximating the total area underneath a curve on a graph, otherwise known as an integral. It may also be used to define the integration operation. This page explores this idea with an interactive calculus applet. Interactive calculus applet.
We can use integrals to find the area enclosed by a polar curve. Here, we use sectors of circles instead of rectangles to calculate the area. Interactive calculus applet.
Not all integrals have antiderivatives that can be written down using the basic functions and operations that we know. Some functions are, in fact, defined using an integral. This page shows two such functions in calculus. Interactive calculus applet.
The integral test provides a means to testing whether a series converges or diverges. Interactive calculus applet.