I'm not a "free range" parent, nor do we live on a farm, so my kids aren't going on the subway alone or milking cows... I think our "more responsibility" for ds10 is in making choices. I try to step back from dictating when he does his homework, or what he has for breakfast. If he has a sleepover, I let him decide on whether he wants to get more sleep or be tired (but not grouchy!) the next day. I do let him walk places alone, or ride his bike, because he's very responsible. I don't let him cook because he's very clumsy. (We've progressed to using the toaster oven and microwave, but that's about it). It's really all baby steps, not some big "now you're ten!" http://www.amphi.com/~psych/responsib.html
I thought that the above link was interesting - there are lots of lists of "chores by age" out there, but this was a very high-level and short overview - things like the difference between being old enough to help out with chores and old enough to evaluate what needs to be done. For our two older dds, learning to think for themselves, helping them to evaluate and process information, was much more important than giving them either responsibility or chores.
Theresa