I just found the kind of soap crayons that my children (and grandchildren) used to write their spelling words on the tub walls. Practicing a few words each day (the ones they are finding harder) helped kinesthetically get the eidetic image of the word into their brains. And it was darn fun!
Soap Crayons Link: http://www.amazon.com/Play-Visions-Crayola-Bathtub-Crayons/dp/B0043BYOO0
We’ve used washable fingerpaint on bathtub walls as well. Bad idea if you have tile walls, though, unless you like Disney grout. Test it out first. We’ve used this on a tabletop too. Roll up their sleeves and use an apron…
If summer weather ever returns, we keep colored chalk in a pail in the closet. We’ve done one spelling word 4 times in each segment of the sidewalk, each in a different color. If they get 100% on their spelling test, try writing them 3 times the following week. The game becomes “How few times do we have to write the words and have you still get 100%?”