First visit if interested should be to the Explore section - http://msdn.microsoft.com/en-US/office/apps/fp123579
- Introducing a new class of apps
- Wondering what apps can do?
- How do apps work, anyway?
Reimagining SharePoint Development - http://msdn.microsoft.com/en-us/office/apps/dn133840.aspx is what made me want to document this and share it. Quick videos to whet your whistle.
Many other videos, training, documents and others.
Apps for SharePoint overview = http://msdn.microsoft.com/en-us/library/office/apps/jj163230.aspx