A great list of 20 different organized "command centers" - amazing inspiration to actually create one myself!
Grafio - Diagrams & ideas - Sweet diagramming app. Tons of features. Might be overkill for younger students. $9.99.
iPad Apps for Marzano's Nine: Cues, Questions and Advance Organizers
Examples of Grafio diagrams, illustrations, vector graphics, mind maps, etc. Formerly iDesk.