MentorMob
http://www.mentormob.com
I saw this tool on Joyce Valenza's excellent blog
Never Ending Search.
I dislike making step by step instructions, because so often the steps change. This tool seems to me to counteract that flaw, because it lets the crowd update the instructions, so theoretically if steps change, someone will catch the error and change the instructions, And maybe that someone won't be me :) I think this may work best with videos, but below I made a step by step lesson plan., which had mostly text instructions
Classroom Ideas:
This might work well as a supplement to lesson plans for substitute teachers, especially if there is much to show from various sources.
This might work well as pathfinder in research projects. In fact, I am going to try this out.
In chemistry classes, this might be a tool for students to explain specific chemical reactions.
In Math classes, this might work in combination with Kahn Academy.