Kid Genius: Site Words app for iPhone and iPad

Help your children learn to read, while spending some quality time with them...

Sight words are the most frequently used words
in everday writing. These words are best learned by, "Sight,"
since it is very difficult to sound them out. Learning sight words
helps you read faster and more efficiently.

Kid Genius: Sight Words, uses the Frys List of words to help new
readers master the high frequency words found in many books. This app is useful
for all ages, but greatly benefits young children learning to read.

You could also potentially use this app if you are trying to learn English.

The words are arranged in 6 levels and each level contains 4 groups of
25 words. The goal is to master each group in each of the 6 levels.