Who has not noticed the things around which remind us of Dharma?
I live in the central highlands of Nova Scotia. Nature abounds here; mountains, hills, bushes, trees, rivers, streams, in the midst of ocean bordered by rock and sand; canopied by every form of sky imaginable; clear, cloudy, colourful, starry, stormy, snowy, wind or calm. It all just sort of melds together in one great display of anitya or inconstancy. All these phenomena are subject to change.
Sitting overlooking Northumberland Straits this morning, I took the opportunity to just sit with the elements around me. The cornucopia; the abundant, overflowing sights, sounds and smells were all present to explore but when finally I had to rise and leave I noticed that where I sat I was surrounded by clover. That little trefoil which is subject to of analogy to many spiritual traditions; a three-leafed symbol of trinities in several forms.
The first thing which came to mind was the Triple Gem; the Three Treasures of Buddha, Dharma, Sangha and so I continued to contemplate. As quickly as the first I recalled the three categories of the path which contain the eight elements; wisdom, morality and meditation. I continued with the three bodies of Buddha; dharmakaya, sambhogakaya, and nirmanakaya. Of course in terms of "threes" there is the flip side of all this, as well: greed, hatred and delusion. But then there are the three types of Buddhas who escape the three poisons; Samyaysambuddha, Pratyekabuddha, and Sravakabuddha. Certainly there are the three vehicles of Buddhism, as well: Sravakayana, Mahayana and Vajrayana without all of which the Buddha Dharma would never have spread so completely; to each according to their need; from each according to their ability.
As if to break the spell and speed me on my way, a bee passed by performing its assigned duties in pollination. I smiled to myself. Here emptiness raised its all-encompassing presence. The symbol I had accidentally selected was without self-nature or inherent existence. Without the bee, the wind, the rain, the sun, the soil and even the winter's coverlet of snow, perhaps this field of clover might not be here. Remove any one of these and clover could only decline, with erosion maybe even cease to exist. It this respect it was not alone.
...and all I meant to do was take a few moments to sit on nature's cushion. Go figure!
My coverage of the "threes" in Buddhism was not exhaustive by any means, but I would be far more interested in YOUR examples of reminders around you, or your expansion of my humble offering.