From the Oracle downloads page, click on "Business Intelligence Suite Enterprise Edition" in the "Middleware" section, accept the "Oracle Technology Network Developer License Terms", and you shall be on your way to downloading the product software. The software is available on "Microsoft Windows" and Linux (x86 Red Hat Linux / Oracle Enterprise Linux, and x86 SUSE) initially, with Solaris, HP, IBM ports expected shortly.
The download takes up 2 CDs - 1.1GB, and includes the following:
# Business Intelligence Suite Enterprise Edition
# Business Intelligence Disconnected
# Business Intelligence Server Administrator
# Business Intelligence Server Enterprise Edition
# Option: Answers
# Option: Delivers
# Option: Interactive Dashboards
# Option: Office Plug-in
# Option: Reporting and Publishing (This is the same as Oracle BI Publisher, v 10.1.3.2.0)
# OC4J Standalone zip file
Oracle BI Publisher is also available as a standalone product, and includes Oracle BI Publisher Enterprise and Oracle BI Publisher Desktop.
I have been running the same software as is now available on OTN, and it is absolutely great :-)