Light Bulb Languages now has accounts on Quizlet and StudyStack. I will be adding links to each activity on the Interactive Games pages for each language next time I do an update. In the meantime you can see the quizzes and vocabulary available and use them if you would like.
Quizlet is useful as it has an app and is therefore easy for children to use independently. I think that StudyStack is more primary-friendly. The activities can be embedded into blogs and websites but there is no direct app at present.
If there is any particular area of vocabulary that you would like a Quizlet or StudyStack activity on, please let me know in the comments (and please tell me which language!!)