One of the activities I set up for my girls (3 years old) last week was to sort various cylinder-shaped containers and cans from our pantry. The challenge in this exercise lies in the fact that the containers vary in two different dimensions - height and base diameter, so they can actually be sorted in two different ways. The kids had to focus on a single dimension to make their comparisons.
They did an excellent job, but sorting by height was definitely easier for them than sorting by base diameter (sorry - didn't get pictures of that one). I showed them how to look down on the containers instead of from the side (which is also good practice for learning maps/topography). I've found that my kids seem to get more excited about 'playing' with household items than toys.
They asked to stack the cans and containers, but I was a little worried about cans denting when they fall on the floor, so I gave them some different food containers to stack:
A morning of Montessori-inspired fun and learning with items from our pantry...
UPDATE: I was so inspired by how much my kids enjoyed early math "games" that I created the La La Logic Critical Thinking Curriculum for 3-6 year olds, which includes online brain challenge games, printable worksheets, enrichment activities and more!