Our school already does a jog-a-thon, and it hasn't done all that well. Plus, I don't really want to compete with current fundraisers run by administration or our PTA, so no cookie dough or cheesecake fundraisers, either.
When my wife was the school secretary, she used to sell pencils, the fancy colored never crazy design ones. She did pretty darn well with that, so I'm leaning towards that as an option.
I'm grateful for the good ideas offered in this thread, everyone.