Some quotes:

"The reason for studying definitions is simple. We need the clarifications in order to get to the top of Motion Mountain, i.e., to the full description of motion. In the past, many
have lost their way because of lack of clear concepts. In order to avoid these difficulties,
physics has a special guiding role. All sciences share one result: every type of change observed in nature is a form of motion. In this sense, but in this sense only, physics, focusing
on motion itself, forms the basis for all the other sciences. In other words, the search for
the famed ‘theory of everything’ is an arrogant expression for the search for a theory of motion. Even though the knowledge of motion is basic, its precise description does not imply a description of ‘everything’: just try to solve a marriage problem using the Schrödinger equation to note the difference." (p769, Chapter III.V)

"In our quest to learn how things move,
the experience of hiking and other motion
leads us to discover that images are produced by charges,
that charges move, accumulate and interact,
and that there is a smallest charge in nature.
We understand what love has to do with magnets and amber,
why the brain is such an interesting device,
and what distinguishes a good from a bad lie." (introduction to Part III, "Light, Charges and Brains.")

Good Flying-circus like constructivist challenges:

Birds come to no harm when they sit on unprotected electricity lines. Nevertheless, one
almost never observes any birds on tall, high voltage lines of 100 kV or more, which transport power across longer distances. Why? (Challenge 1007s)

The shortest light pulse produced so far had a length of 100as. To how many wavelengths of green light would that correspond? (Challenge 1017)

From the Suggestions page on the textbook Wiki:

"Page 323: Maybe it would be nice to add some interesting facts about abacus e.g. competition between abacus and electronic calculator in 1946 where abacus won (http://www.ee.ryerson.ca/~elf/abacus/abacus-contest.html) or link to short youtube clip (http://www.youtube.com/watch?v=wIiDomlEjJw) if it is not against author's policy. (CS: I have lived two years in Japan, and I like Japan a lot; but this sort of sadistic teaching will never have a place in my book.)"

From the webpage, among several open challenges:

"Challenge 5 (April 2006): The simplest unsolved knot problem. Imagine an ideally wobbly rope, that is, a rope that has the same radius everywhere, but whose curvature can be changed as one prefers. Tie a trefoil knot into the rope. By how much do the ends of the rope get nearer? In 2006, there are only numerical estimates for the answer: about 10.1 radiuses. There is no formula giving the number 10.1 yet - can you find one? Alternatively, solve the following problem: what is the rope length of a closed trefoil knot? Also in this case, only numerical values are known -- about 16.33 rope radiuses -- but no exact formula. (Prize value: 200 euro)

Challenge 6 (October 2006): Extending the belt trick to spin 3/2 (suggested by Frank Sheldon). The Dirac belt trick simulates the behaviour of a spin 1/2 particle. What is the construction for a composed spin 3/2 particle? For an elementary spin 3/2 particle? (Prize value: 50 euro)"