Padlet is a website that six graders are using this year to give their opinions on the books that they've read. It is very useful for other students because they get to see what their classmates thought about a book. So they could see if the book is worth reading. In fact, recently my class made it a bit more fun by getting to scan our classmates' QR codes with the iPads and see what they thought about the books they read so far this year and over the summer.
It also comes in handy for the 40 books Challenge to remember what we have read and for teachers because they can see how much you're reading. I think it is the best website to comment on and review books because it lets you explain what you liked about the book and tell special highlights that you liked about the book.