This site explains the derivatives of standard logarithmic and exponential functions. The site has example problems and grades your work, explaining errors you may have made when attempting the problem.

A good site with a definitions and proof of the power rule for both postive and negative powers.

This is a 20 question quiz on logarithmic and exponential functions. This is a good way to be sure you know how to use logarithms and exponents. The site however only tells you if you've made a correct choice, there are no explanations.