Lacking in the "Green Thumb" department? Plant zinnias. They are so easy to grow. You sow the seeds directly into your garden in late spring. No need to coddle delicate seedlings. No need to transplant. They are tough, hearty plants. Ours continued to push forward right through the high winds of Hurricane Irene.
One of my absolute favorites is "Envy". It is a chartreuse beauty.
Growing Tip: Sow seeds once a week for a month to stagger blooming time.