You can download and install one of the free platforms like
Solaris or the free
RHEL clone
CentOS for instance, then you can download the Oracle software for free for evaluation purposes only from
OTN (free registration is required).
Some time ago a
DVD with a pre-installed VM image of the
Oracle Unbreakable Linux and a pre-configured
RAC with
Oracle SE 10g was available on OTN, but I cannot find it anymore.
