Health Technology Assessment Database (CRD)
http://www.crd.york.ac.uk/crdweb/
Cochrane Library
http://www.thecochranelibrary.com
INAHTA Briefs
http://www.inahta.org/publications/
UK National Library for Health (NLH)
http://www.library.nhs.uk/
US National Library of Medicine
http://www.ncbi.nlm.nih.gov/