There is a POX version of the venerable Stanford OpenFlow Tutorial.
The Mininet wiki and, in particular, the Mininet FAQ are also great resources. This is especially true if you’re also using Mininet, but they actually contain a fair amount of generally useful SDN/OpenFlow/networking know-how.
As other resources become available, you’ll find them here! (And, of course, the mailing list is an invaluable resource too!)