Ekr and I have discovered a simple new toy recently: MegaMagz or GeoMags. They're clearly fun for adults, to the point where he and I fought over them one evening soon after getting a small set. Adults can figure out how to make hinges or rotational joints, maximizing the magnetic attraction by the careful arrangement of the balls and bars in certain alignments, maximizing rotational momentum and so on. Yet they're also fun for kids below the suggested lower end of the age range. We gave a set to a 3-year old on his birthday and he immediately constructed a stick out of several short bars, then discovered that his magnetic stick was able to pick up a ball bearing just by getting near it. He named this his "finder stick" and started rolling the steel bearings under the couch so he could then stick his "finder stick" in there to retrieve them. Last week we gave a set to a 4-year old for her birthday and now her mother tells me:

[She] has suddenly discovered that magnets can not only stick things together, but can attract and repel each other. She's been walking around with pieces of the magnetics set you gave her, building things and showing everyone how it works, for a day and a half.

I guess the age ranges they put on toy boxes are completely arbitrary. Sure a three year old can swallow a ball bearing -- but they can also get into far more dangerous stuff. Better just to teach them judgement and motor control by that age and then deal with the occasional mishap (like when I was three and I stuck a bean up my nose and couldn't get it out) with as much calm as you can muster. Somebody on Epinions has similarly ignored the age recommendations -- she recommends Magz and talks about how her four-year-old plays with them.