The Khan Academy is full of great math tutorials. See the section on calculus here
For unique problems and math tools, check out The Art of Problem Solving
I appreciate many nerdy webcomics, like xkcd and PhD comics. Really, though, I love cute animal pictures like those on Cute Overload. For the months of March and April 2012[UPDATED: AND MAY], Discovery Channel is running PENGUIN CAM which of this writing is the best thing on the internet.
