This is the Wild Lily of the Valley (Maianthemum canadense),
aka Canadian Mayflower. The leaves (about 3 inches long) are about the
first sign of green on the floor of the woods. The flowers are
followed by little white berries.
flowers appear on stems that have two leaves (thanks for the
observation, Leigh). The single-leaved plants that cover the floor of
the woods do not have flowers.