update: OpenEd is now ACT Academy
OpenEd is a free website that contains educational videos, games and digital tools for classroom use. You can search by topic, grade level, standard or keyword. Once you find a resource you like you can favorite it, assign it to your students, add it to your Google Classroom or clone it so you can edit it. If you want to assign it your students both you and your students will need accounts. If you are a Google school there is Google single sign on, otherwise students will need to go through the process of creating an account. The advantage to using the OpenEd platform to assign the activity is that there are premade questions that go along with the resources.
I tend to be a control freak and like to make my own questions (or at least edit the ones there). I would probably create my own form where I embed the resource and then ask the questions that I want. The advantage to this is that now I can distribute the form in the same method I share other resources with my students and they don't need to create an account on a new website. While it is nice that OpenEd can keep track of who has mastered the assignments you give, you can also just do that yourself in the spreadsheet that you get as a result of the form.
For me I like it better as a place to search for resources and then put them on my own platform. What would your preference be?