Oracle 11g for Linux x86 has been released and available for download from official web site:
Oracle Database 11g extends Oracle's unique ability to deliver the benefits of grid computing with more self-management and automation, making it easier to innovate faster with confidence using Real Application Testing, manage more data for less with advanced partitioning and compression, and much more.
The following are the operating sytem requirements for Oracle Database 11g release 1:
=> Asianux 2.0
=> Asianux 3.0
=> Oracle Enterprise Linux 4.0
=> Oracle Enterprise Linux 5.0
=> Red Hat Enterprise Linux 4.0
=> Red Hat Enterprise Linux 5.0
=> SUSE Enterprise Linux 10.0
I'm sure you will be able to use Debian or Cent OS for testing purpose.
Download Oracle Database for Linux
=> Click here to download Oracle 11g for Linux