
The Instant Client is free. It has support for OCI, OCCI, and JDBC connectivity. There are versions of the Instant Client for Microsoft Windows, Mac, Solaris, Linux, and many other operating systems. SQL*Plus is available, but it comes packaged separately.
The great thing about the Instant Client is that you just have to unzip it. There is not Oracle Universal Installer to configure it. Just point your ORACLE_HOME to the directory where you have unzipped the files. The Instant Client is the ultimate thin client for Oracle connectivity. I might try to get our project to use this. We have our own set of issues with the fat Oracle 10g client.