Time magazine has been doing some articles on the health benefits of meditation. U Mass Medical Center has some research. You can see it on their site. Jon Kabat-Zinn has spearheaded some of it. His bio on their website says:
Dr. Kabat-Zinn's major research pursuits lie in the emerging field of mind / body medicine, with the focus on the clinical, social, and human performance effects of mindfulness meditation training in various populations. These include people with chronic pain, stress related disorders, and / or a wide range of chronic diseases with a particular focus on breast cancer; multi-ethnic and multi-racial inner city communities experiencing high psychosocial stress due to poverty and associated social conditions; and inmates and corrections personnel in the prison system. Other areas of research are directed at the effects of regulated attention on healing processes; stress in medical education; cost-effectiveness of mind / body interventions; stress related to work and organizational re-engineering; the tao of work; mindfulness in the physician-patient relationship; the development of psychological resilience to stress; mindfulness-based stress reduction curricula and their implementation in the primary and secondary education; achieving optimal performance in athletes through mindfulness meditation training.