Can anyone point me to some good references online where I can learn about Oracle databases?
You can try the Oracle website (http://www.oracle.com/technology/documentation/database.html) there are lots of documentation. Also the Oracle forum would be a good place to keep reading questions and answers
This seems like a good place to get started until you have more specific questions that we can help you with: http://download-uk.oracle.com/docs/cd/B19306_01/install.102/b14316/startrdb.htm
AskTom is a good place if you want to learn more in general and understand when to use particular features. asktom.oracle.com
Check on Tahiti, where the absolute references on Oracle can be found.
Without further information, I would recommend beginning with Oracle Database Concepts.
http://www.oracleoverflow.com/ is a dedicated Oracle Stack Exchange site run by Simple Talk Publishing.