The calculus online community is probably the most important resource available, provided your professor has set it up. I cannot recommend this highly enough. The most useful feature is the forums.

Calculus tutoring is available in APM B402A free of charge and during most hours of the week for all classes up to 20F.

Calculus on the Web seems to have a good interface for trying your hand at a variety of practice problems.

S.O.S. Math has a lot of useful tables; everything from trigonometry, to calculus, and more.

The American Mathematical Society has helpful information on a variety of things, including career opportunities.

Mathworld is an encyclopedia on all things math (try Wikipedia too).