University of Hawai'i
University of Hawaii: Topics in Calculus
Good site on calculus with links to the topics about calculus.
Other
University at Albany: Checking the Divergence Theorem
This site explains how to check for divergence of a vector. It includes formulas and solutions.
Wolfram Research
Wolfram Math World: Divergence Theorem
This site gives proof of the Divergence Theorem. Students should be somewhat familiar with divergence and gradient to utilize this site.
Other
University of Reading: Divergence Theorem
The page is a slide from a lecture showing the notation for the Divergence Theorem.