elysia, have a look at this idea? Even if you were doing a letter a week you could just have one hanging with the letter they are working on and the rest on a shelf or in a basket. The books could be just 4 x 6 inches and the children could draw the things in them.
Reggio. Preschool age children were curious about their heights. Teachers measured them then taught them how to measure a piece of yarn to match their height. Here is the finished height chart, complete with names and self portraits by the pre-k children. Growth Growing Height Chart Compare Contrast Math