Microwave oven, hotspots in music venues and Young's double slit experiment.
A microwave oven transmits microwaves into the oven which interfere producing standing waves. At the antinodes water molecules in the food resonate which heats the food up.
At music venues the sound from the various speakers will interfere which can lead to "hotspots" of sound in some places and quiet areas. The old Wembly Stadium (in London) suffered from this. In the new stadium the windows of the VIP boxes are all slightly out of line which disperses music and cheering more evenly throughout the stadium.
Young's double slit experiment is the classic proof of the wave nature of light. Coherent light is diffracted through two slits very close together. The diffracted light overlaps and interferes producing a pattern of light and dark fringes on a screen.
A slight difference in frequency between two sound waves can cause the effect of beats.
This effect is used, for example, in tuning a musical instrument. Say a guitar, you set up the basic note (La, using a tuning fork) then you tighten the cord until you hear, plucking it, an effect of "weavy" sound" changing intensity periodically (the same as saying "a" opening and closing your mouth).