The point is, don't wait to order the seeds of your dreams. Other items that should not be postponed: signing up for that community garden plot; turning over a new plot while soil is still porous and wet; and, getting your soil tested.
Look below for this writer's current favorite seed sources.If all you plan to do is put a few tomato and pepper plants containers on the deck, skip mail order and buy some plants and a few seed packets at a home or garden center.
However, if you have a good sized plot, and especially if you are looking for heirloom or unusual seeds, here are three of my current favorites. Note: some mail order houses sell very nice live plants.