Some stuff about SP2013 App and Workflows

Whilst working recently on some SharePoint 2013 Apps stuff I came across a number of resources which helped. They might help you too:

Three ways to think about design options for apps for SharePoint
http://msdn.microsoft.com/en-us/library/office/fp179889(v=office.15).aspx

Find how-to content, sample code, SDK and API documentation, training, and technical articles for developing solutions and customizing SharePoint 2013.
http://msdn.microsoft.com/en-us/library/office/jj162979.aspx

Code samples for SharePoint 2013
http://msdn.microsoft.com/en-us/library/office/jj901637.aspx

SharePoint 2013 workflow samples
http://msdn.microsoft.com/en-us/library/office/jj164126.aspx