A presentation I gave at TechEd 2014 (Barcelona) in October 2014. Covers some fundamentals of developing Apps for Office, and shows a sample Word task pane app, which analyzes the current document and searches your SharePoint/Office 365 environment for similar documents. The app also integrates with OneDrive for Business, to allow the user to save links for future reference.
Also, my co-presenter Andrew Salamatov presents some great information and demos around mail apps.
The presentation also covers some common mistakes, and tips and tricks when developing Apps for Office.