what kind of treinament you find? A techical/functional treinament, a user application treinament.
If techinal treinament, the bookshelf is the better document to find information. You can use the forum, sites and Oracle Metalink to find you doubts.
If user application treinament, where user use the application and find about how to execute a process, you can use IHelp or your company can use Oracle UPK (User Productivity Key). You can create treinament in this tool and your users can acess the treinaments.