Calculus-Help.com http://www.calculus-help.com/
Features a new practice calculus problem every week with complete solutions. Includes an archive of prior weeks' problems and solutions.
Mr. Calculus http://www.geocities.com/calculusisnumber1/
"Mr. Calculus is available to give you hints on your calculus/mathematics questions." Contains links to AP resources, tables for derivatives, logarithms, exponentials, convergence tests for infinite series, and sequence limits.