There are many good Oracle - and database - sites on the internet, but many are more for Database Administrators (DBAs) than developers. This is a selection for developers.
First of all, a site that one should regularly check for the sake of one’s sanity.
Symptoms for an urgent need to visit include a strong temptation to denormalise,
a sudden enthusiasm for the latest Object-Oriented XMLobol offering,
a failure to see the link between theory and practice or a
tendency to see everything as trees. Diogenes Laërtius, a Greek author
of (probably) the 3rd century AD mentions in his biography of the Greek
philosophers that another Diogenes, the Cynic philosopher of the 4th century BC,
used to say
that he imitated the choir masters, for that they set the note too high in order that the rest might catch the proper tone.
Today’s Diogenes has the name Fabian Pascal, who runs his own website at www.dbdebunk.com. Chris Date, the Grand Old Man of relational theory, contributes regularly to the site. The quote of the week alone deserves a regular visit.
A site that is very popular among Oracle developers and is on the Oracle site itself, is the section where Tom Kyte answers with his team the questions put to him by developers.
In a similar spirit, the site of Connor McDonald is a very practical one, which targets both developers and DBAs. You will learn a lot from here too. His choice of links is extremely good and can be followed in confidence, but beware that some of the links are extremely technical (as in "nuts and bolts").
Among the links of the preceding site, we are especially fond of the site of Tim Gorman and Jeff Maresh. The papers are of an extremely high technical standard and yet written in an eminently readable, lucid and often funny style.