Here is a link directly to the Winter Sowing forum. It is a very specialized form of growing from seed so the best advice can be found there and you'll find the answers to your questions there. If you do a search there for each crop folks will have posted starting times for you.

Now some of the items on your list - sunflowers, melons, squash for example - are best direct seeded in the garden at their proper planting times for your location. They don't need to be transplants in our zone.

For some of the others, they grow so quickly that you don't want to start too far in advance as they will get so big they have to be transplanted again and again before planting time. So alot of the timing will depend on your set up and ability to move things into bigger pots as needed.

Dave

http://forums2.gardenweb.com/forums/wtrsow