The MS Walk
Held in more than 700 cities nationwide during the spring, money raised from this 5K and 10K event allows the National Multiple Sclerosis Society to assist more than a million people annually. The group also organizes other events, including the MS Bike Tour and the MS Challenge Walk. Call 800-344-4867 or visit www.nationalmssociety.org.

The Susan G. Komen Race for the Cure
Hailed as one of the largest 5K runs/fitness walks in the world, this race is held in more than 100 American cities and three foreign countries each year. Last year, more than 1.3 million participants raised proceeds that help fund important research and health initiatives to treat breast cancer. Go to www.komen.org to find the local affiliate in your area.

The Great American Cleanup
The organization Keep America Beautiful runs the largest cleanup event in the country every spring, drawing more than 2 million volunteers in 35 states. Volunteers search local roads and highways for litter for as long as they like, making it even more challenging than many 5K walks. Go to www.kab.org for more information.

Walk to Cure Diabetes
Held in more than 200 locations by the Juvenile Diabetes Research Foundation, the Walk to Cure Diabetes draws in more than 400,000 participants each year. Recently, the event (which can range, depending on the city, from a one-mile walk to a half-marathon) raised almost $70 million for diabetes research. See more at www.jdrf.org.

The Kidney Walk
This noncompetitive walk is held all over the country from early spring to late fall and is organized by the National Kidney Foundation. It raises funds for dialysis patients, organ transplant recipients, and donor families, and for education about and treatment of kidney disease. Get more information by calling 800-622-9010 or by visiting www.kidney.org.

The Heart Walk
As the signature fund-raising event for the American Heart Association, the Heart Walk promotes physical activity and heart-healthy living in a fun family environment. This year over 1,000,000 walkers will participate in more than 600 events across the country, raising funds to save lives from this country’s No. 1 and No. 3 killers, heart disease and stroke. Join your employer or family and friends in a Heart Walk near you. Get more information by calling 1-800-AHA-USA1 or by visiting www.americanheart.org.

The Leukemia & Lymphoma Society's Team In Training®
As the world's largest endurance sports training program, it provides training to run or walk marathons and half marathons or participate in triathlons and century (100-mile) bike rides. Since 1988, more than 295,000 volunteer participants have helped raise more than $660 million. Get more information by calling 800 955-4572 or by visiting www.leukemia-lymphoma.org.