Using an iPad, smart phone or camera, take photos of SHAPES, COLORS, LETTERS.
The fall is a great time to investigate the changing colors of the leaves or even the different shapes that leaves have.
In the spring, look for new growth or the different flowers that are blooming.
Take pictures of things that are circles: tennis ball, water meter cover, bicycle tire, donut ...shapes are all around.
Look for a specific color, like blue. Maybe you'll find a blue jay, or a blue truck, the dart from a nerf toy, a frisbee stuck on the roof.
Or while you are grocery shopping, have your preschooler look for animals on packaging. The cereal is a winner, but keep your eyes open, you never never know where you might find an animal hiding.