If you or your children are learning how to read and write, you'll definitely want to check out the Dolch sight words charts and flash cards.
The Dolch lists contain English phonetic words (like the word so) and irregular words (like the word to) that new readers and writers need to know for basic reading skills. The lists are for preschool through third grade reading levels and are used by most schools in the United States.
Get them at:
http://www.kristensguide.com/Printables/education.asp