New to Gardening... need advise & suggestions

I live in northern NJ and just dug out an area for a vegetable garden. I am going to build a raised box and fill it by next week.
I would like to plant something now but I know for most of the vegetables I have to wait until Spring. Are there any leafy plants or roots I can plant now for harvest before the frost?
If so, what kind? where would you reccommend purchasing them from?
Again, I'm new so I don't know ANYTHING about this and am trying to learn :)