The Joint Commission on Accreditation of Healthcare Organizations (JCAHO) is the national hospital accreditation agency for the United States. They have a publicly available database called Quality Check, which allows you to search for hospitals and verify their accreditation status. Available is the report of their last review, and the information is very complete.
In March 2005, the US federal government unveiled Hospital Compare. This search engine allows you to search by cCity, state, county or zip code, or for a particular hospital by name. The search engine in not particularly forgiving: if you search by zip code, for example, and there are no hospitals in that zip code, try searching by city. The search engine will then allow you to select hospitals, various conditions (heart attack, heart failure, pneumonia) and selected interventions for each condition. Graphs are displayed that compare your chosen hospitals to state and nationwide averages for that disorder and intervention.
To find the Websites of specific hospitals worldwide, the most useful resource is Hospital Web at Harvard University. Hospital Web links you to Websites mounted BY the hospital or health consortium itself.
Just how useful are these Websites? Bear in mind that all are advertising venues for the hospital; you will only find information that the hospital wants you to find. And, information is not consistent. On some Websites, it is hard to even find something as simple as the hospital's address and phone number.
No matter how good they are, the likelihood of finding out the quality of care in a particular hospital is not very good. For information of this sort, the best Web resource is the US News and World Report annual survey "Best Hospitals."