Certain crystals that can be found in nature, like quartz and calcite, exhibit a very peculiar polarisation trick: if you look through them, you get a double image. This is because these crystals split up the image according to polarisation direction. This property can be exploited in many ways.
Modern TVs, computer screens and phone displays use polarisation technology to create color images. The major advantages of this are that the screens are flat and energy-efficient. But it can make life a little complicated if you often wear polarising sunglasses...
Many centuries ago the Vikings were able to navigate a large part of the globe, even though on the northern seas the position of the sun was often impossible to measure because of clouds and fog. Legends tell of a Viking "sun stone" that would act as a compass. We now know that this sun stone is in fact a device to measure the sky polarisation, which contains all the information one would need to find directions.
Many screens would work like a mirror when the image on it is quite dark: you would see your own reflection rather than the image on the screen. Polarisation tricks can be used to suppress such reflections.
Many professional photographers use polarisation filters to manipulate the appearance of their pictures. For instance, using polarisers yields photos with dramatic looking skies. But polarisers can also be used to suppress reflections in windows or on water surfaces.
Tanks are often painted in the exact green color of the forest that it is hiding in. Even though the color is identical, the polarisation of the tank is completely different from the polarisation of the trees. This enables the enemy to still spot the tank...
3D movies are nothing more than an illusion, enabled by polarisation technology. Various polarisation tricks inside the 3D glasses make that each eye sees an image that is a bit different from the other one.
It is obviously very important to detect cancer as soon as possible, but often the first stages of for instance skin cancer are literally invisible. However, it turns out that the polarisation properties of affected skin regions are different from those normal skin. This allows us to detect it with a polarisation measurement.