I have found the most wonderful site! If you know what zone you are in, which you should from my last post. Then this site tells you what vegetables you can plant and when, in your area.
Vegetable Planting Calender
I live in Zone 6 and by looking at my planting calender, I have realized that I need to start Cauliflower inside in only 6 weeks. So seed buying needs to be quick to allow time for shipping. Off to look for seeds...