The Oracle 11g Release 2 (11.2.0.3) Database Instant Client for Apple OS X on Intel x86-64 is now available for download from OTN. It is supported on the two latest OS X releases: Lion (10.7) and Mountain Lion (10.8). It provides both 32-bit and 64-bit client support.
Oracle Instant Client is a simple bundle of libraries that client tools and programs (like PHP and Ruby) can link with. This allows those tools to access Oracle Databases.
You can really help us justify resources for the OS X bundle if you email me letting me know you are a fan. Since Instant Client is a free download, it is tricky for us to know how widely it gets used. My email address is christopher.jones-AT-oracle.com
Any issues with Instant Client can be posted to the OTN Instant Client Forum.