There are a bunch of these surrounding the linked optical-electrical-magnetic responses of a material, like the Faraday effect. Useful in all sorts of sensors and scientific instruments.
A changing current produces a magnetic field, and a changing magnetic field produces current. This is the basis behind electrical generators and motors, as well as many other devices. A speaker is more or less a membrane with a coil of wire attached to it, with a magnet nearby. When current flows through the wire the resulting magnetic field pushes against the magnet's permanent field, moving the membrane. Do things the other way (i.e. push the membrane, moving the coil through the magnetic field to produce a current) and you have a microphone. Currents moving small magnets also form the basis for many electronic buzzers and switches.
This is on the border of chemistry and physics, but mayonnaise exists because of an amphiphilic molecule (one end attracts water, the other attracts oil) called lecithin in egg yolk. You beat the oil into tiny droplets, which are surrounded by lecithin on their surfaces. The water-attracting bits face outward, and prevent the droplets from joining together into larger pieces. Unless you mix in too much oil for the lecithin to separate, in which case the suspension breaks. There's all kinds of complicated physics underlying food, paints, inks etc. that falls under the label soft condensed matter physics.
LCDs--liquid crystal displays--have, true to their name, a layer filled with a type of material called a liquid crystal. These are either spindle or disk-shaped molecules, which make the material go through a collection of interesting phase transitions even while solid. Imagine a little pixel/block of spindly molecules, all parallel and pointing in some direction along the plane of the screen. By applying perpendicular electric fields to each end we can make the molecules continuously twist 90 degrees as we look from the back surface to the front. This will actually twist light that goes through it. Place two polarizers at each end, and you can now decide whether light gets through the front polarizer or not by applying the twist appropriately. That turns pixels on and off (with varying degrees of brightness with angle) giving you a display.
Glow-in-the-dark toys work based on phosphorescence. Both an electron and a hole (the absence of an electron on an adjacent molecule, leaving a net positive charge in the area) will weakly bind together in a configuration called an exciton. Both the electron and the hole have spin-1/2. These can combine in three ways to yield spin-1 (in which case we say the exciton is in a triplet state), and one way with spin-0 (singlet state). The triplet states don't have any easy way to get rid of their angular momentum, so they're stuck in the high energy state for a long time (more complicated processes being rarer) due essentially only to angular momentum conservation. While the decay of the singlet states will take picoseconds, the decay of the triplet states can take hours: so the substance glows weakly for a long time.
Anti-reflection coatings on lenses work through the principle of interference. The coating, when applied, leads to two partially reflective surfaces on its front and back. If you get the thickness and material speed of light just right you can get the reflections from both of these surfaces to destructively interfere and cancel out.
There's the piezoelectric effect. Flexing some crystals will produce a small current, and vice-versa. The applications list is pretty long.
Stud finders measure the changing dielectric constant inside the wall, which changes the capacitance between multiple sensor plates.
The ideal gas law says that PV=nRT (pressure times volume is proportional to temperature). By manipulating the pressure of a gas cycling through different portions of a winding pipe, the gas can be made hot on one side and cool on the other. Blow a fan over the cold end to distribute the cold air inside a box and you have a refrigerator. (set things up slightly differently and you have a heat engine). In practice you want to work with liquid as well, since the evaporation/condensation process takes up a lot of energy as well, which helps with heat extraction.
SQUIDs use the quantization properties of superconductors to measure very sensitive magnetic fields. Superconductors are also necessary to run things like MRI machines, because they also have zero electrical resistance: the high currents needed to make the strong magnetic fields would melt the machine otherwise.
Antimatter is used for medical imaging in positron emission tomography. You ingest a modified sugar molecule that undergoes radioactive decay to produce a positron (an anti-electron). This then annihilates with an electron nearby in the body, releasing gamma rays travelling in opposite directions. By measuring for tightly spaced signals of oppositely travelling gamma rays, an algorithm can infer where the annihilation took place. and measure the distribution of the compound in the body.