ClinicalTrials.gov is one of the major registries for clinical trials. The International Committee of Medical Journal Editors endorse the use of such registries. Chest for March 2007 contains an article from two members of the National Library of Medicine, describing how to register your trial in this registry.
Your local library can help you with choosing MeSH headings: I would certainly be pleased to do that for people in "my" departments here at Leicester.
The Chest paper is available here: http://www.chestjournal.org/cgi/content/full/131/3/909