While it may be too late to save seeds of your favorite summer vegetable, you might be able to still find seeds from annual and perennial flowers/herbs. Here in Zone 7, we still have seeds ripening on plants so we’re going around collecting seeds for sowing next year.
In our garden, easy seeds to harvest include zinnias, marigold, salvia, moon vine and herbs (basil, dill and cilantro). While many seeds breed true (next generation is the same as previous generation), you may find some interesting mutation in next years plants.
A few years back, we saved some petunia seeds and the following year had some unusual bi-colored petunias. As is often the case, the hybrid didn’t breed true so we missed the chance to create a new cultivar, p. grandiflora ‘heliosmonroe’