CruiseControl is available for download in three distributions:
There are getting started guides for the binary and source distributions.
For further details about the configuration file, look at the Configuration Reference. You can learn more about the various pieces of CruiseControl by reading the overview.
The CruiseControl wiki has a wealth of information, such as detailed scheduling scenarios.
To ask questions or get help with any problems you are experiencing, send an email to the users mailing list.
CruiseControl has been featured in several excellent books:
Pragmatic Project Automation by Mike Clark: An excellent book that covers several automation subjects. Chapter 3: Scheduled Builds is available online as a PDF and has a section called "Putting A Build on CruiseControl" that walks through getting CC up and running.
Continuous Integration: Improving Software Quality and Reducing Risk by Paul Duval, Steve Matyas, and Andrew Glover: this Jolt Award winning book covers a wide range of continuous integration topics.
ClearCase, Ant, and CruiseControl: The Java Developer's Guide to Accelerating and Automating the Build Process by Kevin Lee: by the author of CruiseControl's UCM plugin, this is a book you can judge if it is for you by the title.