Modern Slate

If you're looking for an easy, inexpensive, and portable way for your kids to practice  handwriting or mathematics tables, check out the dollar deal section at the front of Target. You can pick up a lined dry erase board for $1. If you don't have dry erase markers or crayons at home pick up a pack of two medium point dry erase markers for another dollar in the same display area. 

To keep records of their erasable work for a portfolio just snap a digital picture, label it with the child's name and date, and save it to a file. I'd save it online just in case the computer crashes. Evernote, Dropbox, or a private photo account like Snapfish are all good options. Sort by date and then print out the best examples of your child's work to include in your paper records.