I'm not sure what got me started, but I have been studying the origins of Kindergarten lately. The inventor of Kindergarten, Friedrich Froebel, had a very different idea of what Kindergarten should be from what it is now (at least what it is now in America,) but his ideas are still very useful. His method involved giving children a series of twenty "gifts" and occupations that all would build on each other. The early gifts were mostly some combination of blocks that related to each other mathematically, and the occupations would be arranging the blocks, and later on other materials, to make harmonious and aesthetically pleasing arrangements and constructions. Maria Montessori was greatly influenced by Froebel, and so that is why Montessori programs include physical math. Froebel thought that children should do these types of activities from the time they were what we would call preschool age until seven or eight years old. It is a shame that contemporary Kindergarten, as well as the later lower elementary school years, are so focused on academic learning. There is definitely something to the idea that if a child plays with unit blocks, then they will intuitively understand math at a much deeper level later on, and so this argues against the worksheet and drill type instruction that is so common nowadays. Interestingly, it seems that many successful architects, as well as other creative types, went through Froebel Kindergarten programs.
So, all this theory led me to buy some standard unit blocks, and Joseph really likes them. I haven't had too much time to play with them with him yet, but I am really looking forward too it. I do think that our set is pretty basic though, so I am sure that I will be buying some more complicated shapes sometime in the future. You can't build a very interesting road without curves, for instance, and roads are what Joseph likes to build.