CartoDB Academy = The place to learn full concepts on CartoDB. Filled with ~1hr lessons on topics from begining mapping to SQL.
Slide Gallery = A great place to get images of awesome projects to include in your slide decks
Pinterest for Maps = Sample maps in context, good for images and anecdotes
CartoDB Vimeo = Video tutorials and screencasts
GIS StackExchange = The best Question&Answer spot for all things CartoDB. Useful for both you and your students.