Oracle Technology Network (OTN) is Oracle's official, interactive online/offline community for Oracle technical professionals (with ~6 million registrations). It professes to be the world's largest online community of developers, DBAs, and architects using Oracle products and industry-standard technologies (such as Java, Linux, PHP). Registration is free.
In addition to comprising several community-oriented Web sites, OTN is also the sponsoring organization of the Oracle ACE Program (which recognizes nonemployee Oracle advocates for their contributions to the Oracle community) and OTN Developer Days Java/SOA workshops, and publishes Developer newsletters (for Java and .NET). Additionally it offers free downloads of most Oracle products under the terms of the OTN Development License.