you can change permissions on the folders you are interested. easiest way would be through the terminal, but you can do it with apple-I as well.
the thing is, you have to share all the folders above the one you want to ultimately want to share. and the settings depend on whether you want everyone to be able to write to the folder or just read from it...
tell us more specifically what kind of sharing you want to do and where?
edit: ok, one confusion... do you want to share folders with other computers? or do you want to share folders between different users on OS X? if it's the former, then i don't think there's any way you can share more than the way already described in this thread..?