FlowVR 2.1 Manual
For your first steps in FlowVR, the wiki is the best place to start. This is also where you will find the source code, developer notes, changelists and tickets.
After checking out the examples, the manual will show you how to roll your own application. It is as much a tutorial as it is a reference on how FlowVR works under the hood.
FlowVR-Appy is the tool used to connect building blocks (modules and filters) in order to create a distributed application. It replaces FlowVR-App, which has been pulled out in version 2.0.
FlowVR's doxygen documentation is closer to the implementation. You will find it useful if you ever need to dive in FlowVR's source code.