You could do a "rummage sale" where you rent a table or space to those who want to bring their own items in to sale. You charge $10 per table, or space and they do all the setting up. You will have to check to see if your school will allow the use of your gym or cafeteria. If not, many church's have the facilities to do this. Huge money maker if done properly and advertised well. Great opportunity for those who didn't have time to do garage sales in the warmer months also.

If you specialize in this such as a "mom to mom" sale where the only things being sold are for babies and maybe up to 8 years you could charge an admission fee like a dollar. I've been to some in Michigan and the line outside to get in is very long. Again, advertising is the key.