for halloween last year my boyfriend and i turned our dining room into a circus tent...we used orange and purple rolls of plastic table top coverings that you can buy at a party wharehouse store...it looked amazing, if i do say so myself.
i don't know if this link to the pic still works, but if not, i'll post another pic to give you guys an idea.
it takes a while to line up all of the plastic, but you basically create a point in the middle of the room to pin all of the 'top' to, and then pin around the edges of the room. (i know, that doesn't make much sense)
but with a pic you'll get the idea.
we alwasy said that we were going to do the same thing for our kids when we have any.
here's the link to the post...http://www.craftster.org/forum/index.php?topic=30998.msg260565#msg260565