Paper flash cards were okay for my daughter (6) but didnt inspire her to learn her words. We found this app we both love it. I can create custom lists based on the word lists her teacher sends home. I also liked that I could consolidate just the words she needed to learn. She likes earning "thumbs up" and "wings" after she gets it right three times in a row. Its not an app that a kid should do alone since they have the ability to mark thumbs up or down themselves but I would definitely recommend for kids who maybe dont learn as well with old-school paper things.
Mcnerds about Smiley Sight Words, v2.1