Name of App
Skill
Level
Notes
Idea Sketch
organizer

visual map-draw or use outline notes. Different colors and shapes available. Not sure I'd use it with my students.
Popplet
organizer
3-5
free version. Easy to use graphic organizer. I used it for a project and loved it's ease of use. If I had a class set of iPads I would purchase this app so students could save their work.