My 2.5 yr. old grandson seems to be totally facinated by tools and anything mehcanical. When he's in my garage he goes straight to the workbench and tool rack and says "papas tools" and wants to know what everything is. I was installing a facuet today and he sat down by me and start playing with the wrenches and again wanted to know what everything was. He loves to move levers, turn knobs ...
I thought I could make a toy / board with captured large nuts (maybe plastic pipe) so he could screw and unscrew them, old faucet handles, maybe sprinkler stuff ... and other fairly large things he could manipulate. of course they'd have to also be safe.
Thought I'd poll the group for other ideas / links to stuff like that.