We have foam letters we use in the bath, they stick to the side of the tub. These are some of our best sessions, because he is semi-contained!
We also play 'fetch'. So I will hold up the word 'car' and he goes to get his toy car. This doesn't last long sometimes though as he just starts playing with the thing!
We also write in big letters on the whiteboard, and draw pictures. He likes the size I think...