When your rub the balloon on your hair, you transfer electrons from your hair to the balloon. Your hair will become charged oppositely to that of the balloon and be attracted to the balloon. Also, each individual hair has a charge of the same sign as your other hairs, and so each hair will repel the others, making them stand up even more.
A soap bubble however hasn't been involved in this charging procedure. Electrical charge can move within the soap bubble film, however, because water with stuff dissolved in it has charged particles, ions, in it, with the number depending on how much of what kind of stuff is dissolved in it.
If a bubble gets close to the balloon, the electric field of the balloon pushes negative charges away from the side of the soap bubble closest to the balloon, so that they prefer to move to the side farther away, and does the opposite to positive charges. What's left is a net positive charge on the soap bubble closest to the balloon and a net negative charge farther away. Because the balloon's electric field is stronger closer to the balloon, the positive charges on the near side of the bubble get pulled towards the balloon more strongly than the negative charges on the other side get repelled. There is a net attractive force.
(republished on 07/13/06)