Everyone loves a good smoothie, and you'll find they taste even better when they are helping to raise money for the benefit of your organization.
A fundraiser like this works best when used together with another event (such as a yard sale or car show) — you can set up a smoothie booth to provide welcome refreshment for everyone who's attending the main event and earn some extra cash at the same time.
Get hold of an easy smoothie recipe that lets you use different kinds of fruit (and therefore create many different flavors to appeal to as many people as possible). You're going to need a cooler on hand for ingredients like yogurt and milk, and it's likely that you'll need a few bags of ice too.
Ask around the members of your group to see if you can borrow any blenders for the smoothie making. It's a good idea to have some soy or rice milk on hand in case there are people who want to opt for a healthier drink (or who are lactose intolerant).
On top of this you'll need to remember plastic cups, straws, and napkins for the benefit of your customers. The blending can then begin.