Group items tagged

Take or create an online course (many are free) where you can go at your own pace, post questions and have discussions. Upload many types of files.

My preferred means of collecting and sharing links. Fully integrates with Delicious -- which had been at the top of my list until their new stacking system which I find . . . well . . . gross. LOADS of other functionality around groups, discussions, annotations, note taking, sharing -- really well designed and gentle learning curve.

Sign up for the free features for teachers. You need to get approval from Diigo but it adds functionality.

This tool lets you add simple comments to a video, helping to guide students through flipped classroom experiences. It also works with Evernote.