Oracle official website for training and certification is
Oracle University – IT Training & Certification
http://education.oracle.com/
For Oracle Documentation, Library, Forum, YouTube, GO HERE:
Oracle Database 12c Release 1 (12.1)
http://docs.oracle.com/database/121/index.htm
SQL*Plus Discussion Forum
https://forums.oracle.com/forums/forum.jspa?forumID=144
Oracle Documentation Library
http://www.oracle.com/technetwork/
OracleLearning Channel
https://www.youtube.com/user/OracleLearning