Push the furniture in the room where the party will be out of the way. The guests often don't take up every square foot of floor space -- a big or small island in the center of the room will suffice depending on the number of guests. Use your tape measure to determine the length and width of the area your number of guests should more or less occupy.
Purchase a large sheet of 1-inch floor foam. With an electric knife, cut the foam to the measurements you took down.
Lay the trimmed foam down flat on the designated area and straighten it into place. If your floor is very slippery, you might need to use some two-sided tape to keep the foam in place.
Purchase or otherwise procure a large area rug that approximately matches the dimensions of the foam. Place the area rug over the foam and smooth it out. Stick to soft varieties of rug, such as shag, and avoid types with rough fibers that may give rug burns.