In the latest version from trunk (version 188.8.131.5243) there is now direct support for Oracle databases. From looking at the code I would say it is experimental, but if you use Oracle, give it a try and report possible bugs at https://trac.cakephp.org.
Update (2006-12-02): I forgot to mention that the Oracle support has been contributed by Jeff Loiselle (aka phishy).
Update (2006-12-04): The Oracle driver has been removed from trunk and the 1.1.x.x branch. It is still available in the 1.2 branch.