Long afternoon, but finally got it. Hope this spares you some pain:
Installation instructions mainly based on: http://ruby.about.com/od/enterprise/ss/ruby_oracle.htm
Install Oracle Instant Client: mkdir C:\oracle cd c:\oracle Get the following files from here: http://www.oracle.com/technology/software/tech/oci/instantclient/htdocs/winsoft.html and unzip them into the c:\oracle\ unzip instantclient-basic-OS-VERSION.zip unzip instantclient-sdk-OS-VERSION.zip unzip instantclient-sqlplus-win32-11.1.0.6.0.zip
Append the following value to your system path: C:\oracle\instantclient_11_1
Download the following file: http://rubyforge.org/frs/?group_id=256 Run the following from the command prompt: c:\where you saved file>"ruby ruby-oci8-1.0.0-mswin32.rb" Answer "Yes"
Assuming that you have previously installed rails 1.x, copy the oracle adapters manually from: C:\ruby\lib\ruby\gems\1.8\gems\activerecord-2.0.2\lib\active_record\connection_adapters\oracle_adapter.rb to:
C:\ruby\lib\ruby\gems\1.8\gems\activerecord-1.15.6\lib\active_record\connection_adapters and rename it to oci_adapter.rb
Copy the ora.dll & oraociei11.dll from C:\oracle\instantclient_11_1 to c:\ruby\bin
Edit your database.yml to read:
development: adapter: oci host: <your db host>:<your db port>/<your db sid> username: <uid> password: <pwd>
go to http://localhost:3000 expand "About your application's environment" the Database adapter should read: oci
good luck. Next up, trying to get this to work on OSX & Linux. weee, the fun!