Check out webcasts and samples for Office 2013 and SharePoint 2013 App development..

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There are a number of good, short webcasts posted on the Office Developer Center of MSDN:

https://msdn.microsoft.com/en-US/office/apps/fp123626

Also, code.msdn.Microsoft.com has an "office" section with tons of sample apps and projects to look at for different versions of Exchange, SharePoint, etc.

https://code.msdn.microsoft.com/office