Have a look at Oracle Express Edition for Linux. If you just want a quick and easy Oracle installation, I have not updated the document to reflect these changes. Many of us who moaned about the lack of an Oracle version for Mac have found that we don't really need one after all.
Parallels Tools now provides file sharing for Linux, and Oracle provides pre-built VirtualBox demo VMs for download. Ubuntu has become a favourite desktop Linux, and is now supported by Oracle, including a convenient XE installation. Parallels, VirtualBox, Mac OS and every flavour of Linux. Since I wrote this article in 2007 there have been new releases of Oracle (including 10g Express Edition for Linux),