Microsoft patterns and practices group has released a WCF Security Guide. The 689 pages compendium offers a general introduction to Web Service security fundamentals as well as in-depth knowledge about several security threads and appropriate counter-measures.
The Law of Demeter or Principle of Least Knowledge is a design guideline for developing software. It's not rare to see common Rails practices violating it. Luke Redpath brings a way to remedy this by providing Demeter's revenge plugin.