Many modules extend Rules or feature Rules integration, and they are available in projects and sandboxes on drupal.org. Below are topics for each module's handbook on these subjects.
Each project is organized with categories for navigation and management, which makes them very easy to find. The three categories that make finding the code you want very fast are Rules, Examples, and Features Package.
The Feature Package tag is useful for finding packaged configurations that accomplish a basic requirement or multiple sets of requirements using Rules, usually with Views and Entities as well. See, Projects and Sandboxes in the "Features Package" category that mention Rules.
If a project only has the Rules tag, then it very likely includes a plugin.
There is also documentation from some Rules plugins in "3. More Features."
There are also configuration exports and tutorials for D6 and D7 available in Additional Resources, however using individual projects works better than putting code in handbook pages, because code is a lot more maintainable when users can use an an issue queue to improve it and a vcs to manage it.