The National Library of Medicine provides free access to vocabulary standards, applications, and related tools that can be used to meet US EHR certification criteria and to achieve Meaningful Use of EHRs. Below are resources either created by or supported by NLM that can be used for providing patient-specific education materials, e-prescribing, and creating, exchanging, and interpreting standardized lists of problems, medications, and test results.
NLM is the central coordinating body for clinical terminology standards within the Department of Health and Human Services (HHS). NLM works closely with the Office of the National Coordinator for Health Information Technology (ONC) to ensure NLM's efforts are aligned with the goal of the President and HHS Secretary for the nationwide implementation of an interoperable health information technology infrastructure to improve the quality and efficiency of health care.
The official CSS page at the W3 Consortium.
The "Learn & Use" page is crammed full of links to tutorials, articles, and events. The majority of resources are in English, but there appear to be a decent number in other languages as well.