What kind of help?
There is to donate (Collect money to give to a cause, generally to help people)
Sometimes events that are to collect money to be donated may be called benefits
Community service (Unpaid labor for an area, generally cleaning litter and such)
Maybe the old boy scout cliche of walking the old lady across the street? :P
Maybe support? Aid? Save? Assist?
You may need to be more specific as to what exactly they're helping with.