This page lists a series of questions a teacher can use to probe for understanding and capability within students. These questions can be used to help teachers with formative assessment.
This social networking site could be used by educators much the same as Diigo. The one real difference is that Pinterest is a visual space (akin to a pin board) where you can get a sense of the content at a glance and dig deeper based on what you see.
For those who would like students (especially elementary students) to look up news items without fear of getting inappropriate media or glorified atrocities.