I learned this at a conference
Have the children sit in a circle.
Take the ball of yarn and tape the end to the carpet (or just hold tight)roll the ball to one person and have that person roll it to anothe ans son until the yarn is gone. You can use this activity while an assistant reads the story of Charlotte's Web. After the "web" is completed you can tape it to the wall or leave it on the floor. Have the children write words to put in the web just like Charlotte does.
This could also be used with Eric Carle's The Very Busy Spider or any spider story or song.
Good luck and enjoy!