Walking through a craft store, I noticed how many of the little bags of wooden craft parts looked just like the parts of the expensive wooden toys in educational supply catalogs. We found a website that sold these parts in bulk and bought bags of various spools, beads, knobs, and wheels. After checking to make sure none of these were too small, I put the larger spools, knobs, and wheels out for the two and three-year-olds.
The next day, I looked for some materials to add that would make the wooden pieces more interesting, and suggest an activity besides stacking. All the pieces have holes, which means you can stick something inside. And for two and three year olds, filling holes is one of the most engaging activities there is. Searching for what would fit inside, I chose pipe cleaners and wooden dowels.
The pipe cleaners fit in the holes easily, and the children fit as many as they could into one hole, making flowers and rainbows.
The dowels were a tighter fit. The children soon discovered that they could use a dowel to support the spools as they stacked them. And that the dowels fit snugly inside the wheels to serve as connectors as they built makeshift tinkertoys as long as the tabletop and as that were as tall as they were.