Nigel Higson at Penn State University. The best calculus resources on the web appear to be those focussing on history. The history of mathematics site sponsored by the University of Saint Andrews in Scotland is first rate. A good place to start within the site is the rise of calculus . There is also a more modest, but still quite nice, site devoted to Isaac Newton which is worth checking out.
Most interactive applets are barely worth the time they take to download.
Another very interesting project is an interactive edition of Euclid's Elements . Many of the animations and illustrations that I have in other parts of this homepage come from here . Here is a list of common errors made by calculus students. Calculus modules I didn't study it carefully, but this Calculus modules online appears to be a sort of online calculus study course. You may or may not find it a useful supplement to the lectures.