Google has searched the wide, open Web for years. They do not index your Google Docs for general consumption, though. However, if you make your Google Docs publicly available – you can share them in a variety of ways in your account – they can be discovered using focused searches on Google.
The Google Operating System blog describes the types of searches. The content is already in the Google index. These tips just describe how you can focus your search to retrieve only files that are shared publicly in Google Docs (documents, presentations, and drawings). It is a nice use of the Google site: operator.