I loved doing this when I was learning how to read and write! Have the child say the individual letters as they trace them in the salt/cornmeal, and you're addressing all three learning styles: visual, auditory, and kinesthetic.
Dollar store photo albums... Turn them into flashcard fun! Easy to write and wipe, just insert what you are working on. You could even just insert white paper and have them work on writing sight words, so many ways to use them!
Kindergarten RTI: Letter Identification & Recognition. Very cool letter book. Lexi is no where CLOSE to Kindergarten, but this is perfect for her level right now. This would def keep her happy on the road trips too.