This game takes a bit of preparation, but is less rowdy than some other "hunting" games and is generally enjoyed.
You will need:
One of two balls of wool (yarn)
How to play:
Start by cutting many lengths of wool. You can vary the length and colour if you wish, but aim for about 8-10 for each child, or perhaps more.
When the children are out of the room (perhaps when they are eating), an adult or older child should hide the lengths of wool around your party area - either inside or outside), so that a short length of wool always shows. Depending on the age of your party children, you can make the "hiding places" more or less tricky - but the game is more fun if the children can't immediately tell how long the piece of wool is.
Call the children inside and start them hunting for the wool. The important thing is that they must always tie their wool together before hunting for another piece, and, once they have touched a piece of wool, they must tie it on. In other words, they can't just search for the long pieces and leave the shorter pieces for everyone else!
After a certain amount of time, or when you think all the wool has been found, call a halt. The child with the longest piece of wool wins.