Sight words are words we recognize without much thought. Many of them don't follow the rules of phonics. Developing a good sight word vocabulary helps children read quickly, confidently, and effectively. If your child is struggling with reading tests, try working on sight words. Students who can read without stopping to figure out individual words have a better understanding of what they're reading. The best way to learn sight words? Repetition.
The Fry Word Lists were developed by Dr. Edward Fry and are considered to be the most common words in printed in texts in the English language. They are broken down by frequency, not grade level (so the first 100 are the 100 most common words in print).
Education.com has fun sight word games that are free. You have to register but the site is free to families.