Here are some useful links for Oracle Certification Online Pratice Quiz and Tutorials
www.geekinterview.com/quiz
You can practice, evaluate your Knowledge on various
Oracle Cerfication Exams and get assessed for FREE.
Quiz Questions are generated randomly.

Oracle Database Skills Practice Test
http://www.geekinterview.com/quiz/Or...tice-Test.html

Oracle8i: New Features for Adm Practice Test
http://www.geekinterview.com/quiz/Or...istrators.html

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Oracle 9i Tutorials
Oracle 10g DBA Tutorials
Oracle Apps 11i Tutorials

Hope these helps you...

Thanks,
db_Wiz