I have been trying to learn how to knit off and on for several years now. I have several friends who are great at knitting and really get a lot of joy out of it, but I only do it sporadically (working on the same scarf for a year now), so I have to relearn the techniques pretty much every time.
I think it's a great idea to teach kids how to knit early on - it's such a calming activity, you can do it while doing other things like watching a movie, you can use it to make all kinds of presents for yourself or others, and it's actually a craft with a lot of socializing potential!
I saw this neat tutorial for teaching kids how to knit on one of my favorite sites, Imagination Soup. This particular tutorial is by Melissa Taylor. I hope to teach my son when he's a little bit older!