What you can still start from seed depends on when your last frost date is.
shows a huge range of last frost dates in NJ from April 26 to June 6. It's a small state to have a range like that! I don't know which applies to you. But figure out your date and count back from that.
I start tomato seeds indoors about 8 weeks before my last frost date. Other things that are started about that time include basil and other annual herbs like dill and fennel. Peppers you are best off buying at this point, because they are so slow to germinate and grow. I start mine about 12 weeks ahead of last frost date!
Squash, melon, cucumber I start just a couple weeks before average last frost, because they can't go out until soil warms up. They could be started indoors as late as at the last frost date or you can just wait and plant them directly in the ground once the soil warms up. Beans I just plant out doors after danger of frost is passed, but they could also be started indoors a couple weeks ahead of last frost date.
Lettuce, spinach, swiss chard, carrots, peas, I just plant the seeds directly in the ground, as soon as the ground can be worked, which for me is about 6 wks ahead of average last frost date. If you are now less than 6 weeks from your average last frost and your ground is workable, you could go ahead and plant these right away; it's not too late.
Broccoli and other brassicas (cabbage, brussels sprouts) I start indoors about 12 weeks ahead of last frost date, because they get transplanted into the ground at least a month ahead of last frost. They are very cold tolerant, but don't do well once it gets hot. You would be best to buy plants of these and put them out now (ish, depending on your frost date).
Hope this helps some; I'm not a new england grower.