It’s not too late to raise money for the National Multiple Sclerosis Society (U.S.) by participating in one of their walking and/or biking events. MS walks start up again in September and October in different regions of the country. You can walk as an individual or as part of a team, and you can also volunteer at the events. Check out this link to see if any are in your area: Walk MS itinerary.
Bike MS, another fundraiser, is for bicyclists who are complete novices as well as Lance Armstrong types, and everyone in between. There are easy, moderately difficult, and challenging courses. Again, you can bike as part of a team (many companies do this) or individually. You can also volunteer and encourage/provide snacks for the bicyclists at different stop points.
For both fundraisers, you can have people sponsor you, or just donate individually the day of the event. The choice is up to you. I’ve volunteered at both outings and they are very upbeat and inspiring. It’s great to see so many people out raising money for multiple sclerosis.