Fiori Mobile: Resources
Many of the Fiori Mobile specific blogs were written by Britt Womelsdorf, such as this introduction and this guide to building apps directly from Web IDE. There is also a guide to deployment. In March 2017 Britt updated us on some new features, such as launchpad apps with multiple tiles. Britt maintains a list of resources too. Mark Wright has written about how to add offline capability to the Approve Purchase Order Fiori app.
Cordova Hybrid Apps
Daniel Van Leeuwen has written a large number of great blogs, in particular about Kapsel plugins. There are too many to list them all but examples are the ones on push, offline, and general tips. Note that most these blogs are written with regard to the local HAT build, not the cloud build from Web IDE (a la Fiori Mobile). The information is still very useful though.
Mobile Services, Offline
For the back-end support for offline I recommend this excellent blog from Andre Fischer entitled How to Implement Basic Delta Query Support in SAP NetWeaver Gateway as well as this guide: Implement Delte Query Support in SAP Gateway OData Services.