Invite your friends and supporters to bring in unwanted items, maybe unwanted Christmas gifts, or any bric-a-brac, collectables, antiques or disused items, you can also visit local shops and traders asking for donations of items, and then sell them by auction.  This works really well if you have a charismatic auctioneer who can entertain the audience and get the most for the lots.  They are popular  so you can expect a good audience.  Don’t forget to sell them teas and coffees as well.