Shmoop has got it all!
I love Shmoop, I have used it for years with high school freshmen and I highly recommend it for all content areas.
How I Use It
I would pose a guiding question (or questions) for my students to find answers to on designated Shmoop pages. I did this to build background on a topic prior to an inquiry unit. Shmoop has so much content that I could use it again and again for different topics, whether I was introducing an author or a time period or a piece of literature. Since my students were familiar with the site and how it worked, it was a great resource to use again and again. There are free kitschy quizzes and students could earn shmoints, this is great for those advanced kids to play with while other catch up. In short, Shmoop offers quick, funny and insightful insight on many topics, they make content fun, relevant, and easily accessible for kids.