I teach at an independent school and we had several days worth of orientation just crowd sourcing all of the tools people have tried. Here are some of my favorites:
If you have access to the Google Education Suite, Google Jamboards are a really neat way for students to collaborate on a virtual whiteboard. Bonus is that it integrates well with Google Classroom.
A web-based app called Hypothesis (https://web.hypothes.is/) is an interesting tool I'm using to have students annotate and engage with text collaboratively.
Padlet is a neat tool where students can post responses and then they can be sorted, color coded, etc. When in-person I do a lot of activities with sticky notes where students put down their questions and ideas and then we sort them, create timelines, models, etc. Padlet seems to be a good virtual tool for that.
Quizizz is one I haven't tried myself yet, but it was demonstrated for us by a colleague and it seems like it could be a really useful tool especially for formative assessments on content.
EdPuzzle is a tool that allows you to embed questions into videos at strategic points. So if you assign a YouTube video for example, you could put questions that check for understanding at certain key points.
Finally, something I am really liking so far is digital interactive notebooks using Google Slides. There are lots of videos available with examples, you can find free templates and paid templates on Teachers Pay Teachers. So far I'm finding that they take a long time to create, but once you've created them, they make life a lot easier!