Prof. Miki is a good app to use with preschoolers and some kindergarteners and first graders. Even the very young will benefit from its gentle and consistent teaching about the many forms that numbers can take and the relationships between the numbers.
City Nights is a cute ebook with a soothing poem that would be perfect for use as a bedtime story. Children can watch as the busy city settles down for the night and help put the sleepy young main character to bed.
Go beyond just teaching kids to count with this interactive number grid that allows them to place numbers from 1 to 100 both randomly and using a pattern to improve their counting and skip counting skills.