Taking a taxi is expensive - if you negociate with the driver beforehand, it is around R$ 75. If you pay by the meter, R$100. If you are unsure, take a prepaid cab from the booths (blue or green). There are lots of hawkers for taxis in the airport - if you are an obvious tourist, you run the risk of paying way too much.
You can also take the "Airport Service" shuttle buses. There are several different lines: Eldorado Shopping Center, to the main hotels, to certain city areas, etc.. The price is R$24 per person (around US$12).
Finally, if you are travelling with little luggage and a tight budget, you can take the shuttle to the nearest metro station (Tatuape) for only R$3 (US$1,5). This is on the blue line - but don't worry, there are maps on the station showing how the different lines connect.

