Diigo is a wonderful site. It is a social bookmarking site, but its more than that. You can also annotate, highlight, and leave post its on the sites you save.
I have been using it to organize my sites for the presentations I am working on.
Edcanvas is an equally impressive site. With it you can put together a lesson with many different resources. Files, videos YouTube or otherwise, pull from your google drive or Dropbox, link to websites that help clarify your subjects, you can even embed your educreations screencasts.
You can follow them both at @diigo and @edcanvas on Twitter. I highly recommend giving them both a try. Well worth it and they’re both free!
O's Bureau of Scientific Investigations 