Thanks to gardener-blogger Tracey at Life in Sugar Hollow for posting this bit of info from the Johnny's Selected Seeds newsletter. I had inadvertently deleted the newsletter, and despaired of finding this list again. According to Johnny, you can still plant in June from seed the following:
HERBS - Basil, borage, calendula, chamomile, chervil, cilantro, dill, epazote, flax, marjoram, milk thistle, parsley, poppy, savory, shiso, and spilanthes.
FLOWERS - Ammi, calendula, centaurea, cleome, cosmos, grasses, hyacinth bean, marigold, morning glory, nasturtium, phlox, poppy, reseda, salpiglossis, scarlet runner bean, snow on the mountain, sunflowers, tithonia, and zinnia.
VEGETABLES - Beans, beets, carrot, corn, cucumber, endive, escarole, kohlrabi, kale, lettuce, pumpkins, radishes, spinach, squash, and Swiss chard.
Living here in lovely Maine, planting in June is a must! Now, off to Johnny's to pick up a few more flower seeds :-)