I was toodling around on the web, looking for something totally not related to this, and found an Excel program that helps you know when to start your seeds. It is very cool.
You will need to know what your frost free date for your area is, but there's a link right on the chart to help you do that.
What a cool tool! No more guessing! And it shows I still have time to order those seeds I've been procrastinating about. Better get on it!