College professor Dan Bach offers a review of the calculus concepts of integrals and vectors. Examples and animated graphs are provided.

This site introduces Riemann definite integral on the closed interval of real. If you are interested in exploring definite integrals, this site may interest you.

The integration tool integrates and graphs functions that student enter into the tool. The tool uses the trapezoidal rule, Riemann sums, and Simpson rule to integrate the function.

University of Tennessee provides this tutorial site explaining summations and how to evaluate them on a TI(85-86) calculator.