How quantum weirdness affects the human world.
Quantum mechanics has long been described as a theory of the very small. We have acted as if the "weirdness" of the quantum realm vanishes when seen in the classical realm; that is, our scale. However, we also know that quantum weirdness does have nontrivial effects on the macro-scale. I call these effects Macroquantum Effects, and the quanta exhibiting them Macroquanta.
Among these are:
Superfluidity and Superconductivity: related phenomena, both of these are where Bose quantum statistics permit frictionless fluid flow. (Of Helium-3 or electricity, respectively.) The lack of individuality of the boson yields macrofluidity.
A speculation: perhaps fluidity in general has quantum aspects? Perhaps water is a quantum fluid! Note synchronous growth of snowcrystals, paradoxical contraction of melting ice, etc.
Shroedinger "kitten", or bilocational ion: some physicists have, by magnetic-ion-trap and microwave-irradiation, placed a single atomic ion in a bilocational state; that is, its probability wave function is bimodal! This is a atom in two places at once, by quantum weirdness.
Bose-Einstein Condensate: At microkelvin temperatures, atoms sometimes merge into a collective state; a "macro-atom" consisting of many atoms in the same wave state. This happens for atomic isotopes with even spin; i.e. bosons! This is Cryogenic Particle Chemistry.
EPR correlations: Quantum particles, once they meet and interact, sustain quantum phase relations even after the interaction is long over. Photons in "doublet" states will interact with pairs of polarizing filters as if they were acting as a unit, not separately. These "EPR correlations" are not classically observable, being hidden in the quantum noise.
Solidity: This prosaic effect depends on Fermi particle statistics and the Pauli Exclusion Principle! Solids cannot interpenetrate because electrons (being fermions) cannot share orbits; the orbitals occupy space and so tend to exclude each other. Solids are solid only because the electron, though point-like, really is "smeared out" all over its orbital.
Stability of Atoms: Electrons do not spiral into their nuclei because they eventually find their lowest energy state - which is not exactly at the nucleus because of the Uncertainty Principle.
Quantum Optics: physicists report that they can use a kind of quantum-wave interferometry to detect the presence of objects without interaction with any photons. To be more precise; they use a fraction of a photon's wave function to scan the object; the difference between free and obstructed wave paths is detectable by quantum interferometry. The photon very rarely actually impinges on the object; but by property recombining it, we can see what it managed to avoid.
I consider this last one very promising indeed; for it suggests using quantum mechanics to get around the one-quantum measurement limit; which suggests a classical subquantum realm. I call this subquantal illumination "sidelight", "virtual light", "psi light", "indirect light", "night sight", microquantum optics.
Perhaps we could combine these macroquanta. For instance, make a Bose-Einstein condensate, then put it in a Shroedinger Kitten bilocational state. Being bilocational, its two modes are in an EPR resonance. The bilocational correlation can't be seen by whole-quantum light, for real light can only move at the speed of light. But perhaps indirect light can see a bit more. Is shadow faster than light?
(See "Quantum Seeing In The Dark", by Kwait, Weinfurter, and Zeilinger, Scientific American November 1996, pp.72-78)