PCRM (Physician's Committee for Responsible Medicine) offers a "21-day Vegan Kick Start Program" that begins the first day of every month. However, you may register for it at anytime during the month.
If you're interested in exploring the health benefits of a plant-based diet, it only requires a name and email address to register. For 21 days, you'll receive an email which will include meal plans, grocery lists, shopping guides, celebrity tips, video clips, nutritional guidance, a community forum, and a personal health tracker (which monitors your blood pressure, weight loss, blood tests, etc for the year). However much or little you decide to participate, it's loaded with lots of educational and encouraging information!