The ability to access virtual manipulatives is a necessity in the classroom for our kids. One of the biggest benefits of each student having their own device is the fact that the kids could just open a new tab when working and access the resources needed to set themselves up for success. However, On our chromebooks, the math virtual manipulative sites/resources are limited.
So... we've created many templates on Google Drive. Google Drawings and Google Presentations provide a great "canvas" of sorts for kids to work with as they learn. Students could turn in their work for teachers to be able to view and understand their thinking.
Here's Just a few templates:
Base Ten Blocks
Ten Frame MAT
Glencoe Manipulatives is a site worth going to. We've had a lot of success with this one.
However, I just came across this new one: Math Learning Center Apps.
Our mathematicians may engage with these sites just for the sake of additional support. However, we often hold our students accountable and do so through having them take a screenshot or even screencast over their work. They may share with their teachers & peers, reflect upon their thinking and more... the sky is the limit!