Last year my students did a webquest on English speaking countries. They showed their findings in presentations that they delivered to their peers in the classroom. I uploaded some of their presos to my Slideshare account (I still have more than a half to upload). One of their tasks was to create interactive quizzes in power point, which are absolutely meaningless on Slideshare.
However, last week I came across QuizSlides, a great tool for ppts. QuizSlides enables you to keep interactive ppt multiple-choice quizzes interactive. QuizSlides is still in Beta and it's still free (The authors are planning to introduce premium features in the future, unfortunately.)
Via Evdokia Roka, Informatics