We let our hotel arrange for a car with a driver to go to Taal Volcano. We paid 5000 pesos (around 100 in 2006) for 8 hours.

There's an official tour service at the dock, where they launch the boats to go to the volcano, but there will be people around the area offering the tours for cheaper price. Once you get to the island, there are also horses for hire if you do not want to walk to the crater.