Perhaps it's not excactly what you are looking for, but I've seen a PPT from Gavin Payne. His last slide mentioned these references/reading materials:

Oracle 2-day DBA Guide (download)

Oracle – A Beginner’s Guide (Oracle Press)

Oracle for SQL Server DBAs (Oracle Press)

I myself liked the first one really well to get me on the way. Unfortunate (or happily ;-)) I have not worked with Oracle in a business environment, so I frgot a lot of what I've learned back then.