Here are links to several tools that I have found helpful for Calculus

1) Slope Field Calculator: This creates a printable slope field. You can also enter an initial value and see how it follows the slope field.

http://www.mathscoop.com/calculus/differential-equations/slope-field-generator.php

2) Numerical Integration: This site includes tools to calculate left, right, and midpoint Reimann sums, Trapezoidal Rule, and Simpson’s Rule areas. It’s not pretty, but it makes quick calculations.

http://nastyaccident.com/calculators/calculus/

3) Calculus Videos: This site contains videos on almost every calculus topic. These can help if you need more examples.

4) Visual Calculus: This has some good tutorials and examples:

http://archives.math.utk.edu/visual.calculus/