Anything that allows you to make extra attacks during the full attack action gets you extra sneak attacks as well: fighting with two weapons, the haste spell, and the monk's flurry of blows are the most common ways of getting extra attacks.
Remember the earlier note about invisibility effects, however. If you're relying on invisibility to set up a sneak attack, you'll only have the effect for the first attack you make during your turn. You'll still get all your extra attacks, but only the first will be a sneak attack. You don't have this problem if you're using a greaterinvisibility effect.