I think computer programming should be taught from early grades, both in order to expand the mind and to be able to use the computing tools around us more effectively (it's no harder than cursive handwriting, and so much more useful!). And then I came across Hour of Code, which is an attempt to introduce kids to programming in an hour during Computer Science Education Week (Dec. 9-15). I hope to run an afterschool Hour of Code event at my kids' school for grades five and six.
I tested the "Write your first computer program" tutorial on my 11-year-old daughter, and she completed it in half an hour, so it seems right for children her age, though she wasn't deeply excited about it. (But it did frustrate my 8-year-old son.)
My daughter then went for the "Create a holiday card" activity with Scratch, and made an animated Christmas card. Scratch is an event-driven graphical programming environment for kids that reminds me a lot of Hypercard (which I still have a full version of on our Powerbook 190 laptop). Scratch has her hooked. I tried Scratch with her about two years ago, but the computer we were running it on was a bit too old and we didn't see the nice little intro they now have for Hour of Code, so it was frustrating. It helps, of course, that she's done some Mindstorms programming before.
Both of the activities were web-based. They're still in beta, but I highly recommend them for kids. There are lots of other activities there. And it's not too late to volunteer at your kids' school to run an Hour of Code activity for them.