I've just published a couple of OUD plugin examples to help customers develop their own extensions.
The ZIP package includes 2 plugin examples to demonstrate the richness of OUD plugin API. The FilterDistributor can be used to route bind request to 2 different workflow elements based on a condition present on the user entry about to be used for authentication. The PasswordSchemeUpgrade can be used to migrate passwords from one storage/encryption scheme to another.
Plugins examples are available at http://www.oracle.com/technetwork/middleware/id-mgmt/learnmore/oid-demos-182820.html
OUD Plugin API reference is available at http://docs.oracle.com/cd/E49437_01/apirefs.111220/e38583/index.html
OUD Plugin Developer Guide is available at http://docs.oracle.com/cd/E49437_01/doc.111220/e38455/toc.htm