While I haven't had a chance to clean up the code, folks have asked for it, 
so I'm making my Perforce implementation for CruiseControl available. 
There are some important notes:

* You need to set up your project manually, you can't do an "add" via CruiseControl.
* Some work needs to be done on the text retrieval for checkin messages, and how 
that's displayed on the CC.rb results pages.
* I haven't used this since August 2007, so cannot vouch for whether it works with
current versions of Cruisecontrol.rb.

Licensed under the MIT license.  I have not yet submitted it to the CC.rb folks, 
as I hadn't had time to clean it up yet. So, if you dial it in better, please do 
submit it to them, or send me a pull request, and I'll submit it, etc.

To install/use it, ut the perforce.rb file into your cruisecontrol/app/models directory.

Manually setup your project:
* Create a directory under the cruisecontrol/projects directory.
* Place a cruise_config.rb file in it. It should contain something like the following 
in order to use Perforce:
 
  Project.configure do |project|
    # Use Perforce for source control
    project.source_control = Perforce.new(
      :port => 'your.perforce.server:1666',
      :clientspec => 'clientspec-for-cruisecontrol',
      :user => 'buildusername',
      :password => 'builduserpassword',
      :path => '//depot/path/to/your/rails/app/...')
  end
  
* Sync your code once.
* Fire up CruiseControl, and let the games begin.

Usual disclaimer: I take no responsibility for your systems, code, etc. Read the code, 
test it out, backup your systems, etc.