As those of us who work in clinical research know, there’s always another study that needs volunteers and never enough volunteers for that study.  If you’re wanting to volunteer for a study, you can always check out ClinicalTrials.gov for information about current studies worldwide.  This site is a registry and results database for federally and privately supported clinical trials.  This site, developed by the National Institutes of Health, was designed to provide valid and correct information about clinical studies.