The
Trailing instabilities section has good images of the Karman Vortex street.
The
Gyroscopic precession section tries to explain the mystery of precession. R. B. Fuller was fond of saying that precession is the hardest to explain because it the one motion we can't experience with our own bodies.
Precession is also mysterious to the vBulletin spell checker which also spellchecks 'vBulletin).
I especially appreciated his method for repeatable launches of the card.