Cool Math
Coolmath: Rational Functions More on Limits
Explanation, examples, and independent practice of limits.
Paul Dawkins
Paul's Online Notes: The Limit: Practice Problems
Practice exercise features six problems that review limits.
Khan Academy
Khan Academy: Determine the Domain of Functions
Determine the domain of a function according to the algebraic limitations of that function.
Math Medics
S.o.s. Math: The Derivative
This lesson does a nice job of clarifying what it means to find a derivative. The lesson gives an algebraic method for finding the derivative using limits and offers a geometric interpretation of the derivative.