Learn to make an easy and imposing Halloween mannequin from PVC for about $6. It packs flat (doesn't add to your clutter), and holds costumes in ways sure to get a lot of attention from your halloween audience.
Once materials are gathered you can make this in about ten minutes, and kids can help!
for contributed photos, more detailed instructions, variations on this theme, PVC resources, and links to other PVC mannequins.
Some of my Halloween work is also in other instructables:Godzilla / T-RexGeneral Grievous with Mechanical Arms