This team of teachers from the National Teacher's Academy did an excellent presentation at the EdTechTeacher iPad Summit. This site lists some of their favorite tools, apps, and sites.
allows presentations to be uploaded to a free teacher account (PPTx or PDF and only 2 at a time) that can be viewed on any device when a presentation is live.
This free version combines electronic and paper assessment for quick grading. Teachers can access pre-loaded Common Core standards and create unlimited answer sheets.
What Did We Do Today? (WDWT) is a mobile platform for sharing class events with teachers, parents, and students to track assignments, reminders, homework, etc.