We use Ipad apps to promote letter writing as well. This app is called Iwrite words. It is an interactive way to have the students write letters.
We have used snow(really shaving cream) to hid letters. Then students were asked to use their pointer finger to trace the letters. This was a fun way to promote left to right progression and letter awareness.
We have HWT letters on rice trays. The children use their fingers to move the rice to reveal the uppercase letters hidden in the colored rice.
Along with these hands on activites, we use handwriting books, songs to promote letter formations(ie;"Where do you start your letters?), and building Mat Man. He is a man that is formed using big and little lines and big and little curves. The children love him.