[Splines]

I did the same thing, and my son was around the same age.

Now we just cultivate whatever interests he has, and try our best to answer any questions he has. He's interested in marine life, but is a bit too young to help out at the Seattle Aquarium. We've enrolled him in a few robotics classes and a programming class that used Game Maker [1]. He loved the Game Maker class, I'd bet that it was a gentler introduction than what I tried with Scratch.

FWIW, he's into video games too (we have a 360, NDS, Wii, PC), but we limit his time and prioritize digital entertainment last.

[1] http://www.yoyogames.com/make