Here is a link to a useful new (2011) report called Best Practices for Mixed Methods Research in the Health Sciences.
Citation: Creswell JW, Klassen AC, Plano Clark VL, Smith KC for the Office of Behavioral and Social Sciences Research. Best practices for mixed methods research in the health sciences. August 2011. National Institutes of Health. Date retrieved. http://obssr.od.nih.gov/mixed_methods_research