P, NP, and Friends. A whole undergraduate complexity course in one HTML file.
For those of you who already know this stuff: forgive me for boring you. For those who don’t: read, learn, and join the Enlightened.
Note: The comment section was down all day, but it’s back now. Google ought to be ashamed to be running something as rickety and unreliable as Blogger. Well, I guess you get what you pay for.