check out this website for all subjects and grade levels. This is a resource I use frequently in my classroom- particularly for social studies. You can sort by resource type (video, lesson, document, etc.), subject, and grade level. A series of videos on this website I've found most helpful is "crash course" (it's like a video version of CliffsNotes).Search for "crash course" and you will see videos ranging from civil rights to planets. Also, most of the videos hit that 10-15 min sweet spot.
need to research this for use in ABE classes
gives some lesson plans and good ideas for using Diigo in classrooms, has some high school level lesson plans
Rap covering improper fractions, long division, some other topics
contains a slide show of some very cool ways to use wordle for all kinds of things - not just math