Use engaging videos on TED-Ed to create customized lessons. You can use, tweak, or completely redo any lesson featured on TED-Ed, or create lessons from scratch based on any video from YouTube.
This is the best resource I have found for additional resources for Google Apps. It includes information about Google Translate, Picassa, Sketchup, Search, Youtube and Alerts.
I've featured VideoNotes a few times over the last year because it is a good tool for building discussions around YouTube videos. It's a great tool, but it doesn't work with videos that aren't already hosted online. Vialogues is a free service that allows you to build online discussions around videos hosted online and videos that you have saved on your computer.