The Customer Knowledge Exchange provides a channel for customers to showcase their expertise and to share their knowledge about Oracle products. Your contributions to the Customer Knowledge Exchange are highly valued by customers, partners, and employees and are viewed by over 300,000+ total users worldwide.
Refer to Metalink Note 375443.1 for details about this program.
Currently there are 3 major forums:
Database / Server
EBS / Applications
Do go through the papers submitted by customers to learn what they learnt. You could also submit your own paper which will be published as a Metalink Note, if it is accepted by Oracle.