wow, the free Oracle starter database version - called Express Edition - has reached production state! In my opinion it has never been easier to get an working Oracle database installed on Linux. The download is just 220 MB large and you won`t belief it - it comes as an RPM package! Hey, and it already includes a nice web interface, which makes it easy to create small database driven web applications:
You can find more information on the Oracle Database 10g Express Edition homepage.
Finally there is also a new version (1.3.21) of TOra - Toolkit For Oracle which also works quite well with the Express Edition. You can download TOra from tora.sf.net
[Update 05. Apr 2011: Please see also my new post: Oracle Database 11.2 Express Edition Beta]