Everything has a natural frequency at which it vibrates. For complex objects, it depends on a complicated relationship between size, shape, density, and elasticity. For some simple objects, however, we can predict what that frequency is.

If you put a wave on a string at just the right frequency, the result is a standing wave like the one in the following video.

If you blow across the top of an empty soda bottle, you make the air inside vibrate. Depending on the size and shape of the bottle, you hear different resonant frequencies.

There was a suspension bridge across a river near Tacoma, WA. When they built the bridge, they didn't take the high winds in the area into consideration. The following video shows how the wind resonated the bridge. This is actual footage…No Photoshop.

Needless to say, they now test bridge models in a wind tunnel.