We had one and a half days in Rio (December 2008) - much to do in a short time. We learned about Martha Vasconcellos here on this website - and contacted her. She is a licensed guide and although she had recommendations for must-sees, she easily customized the itinerary to match our interests - and flexible enough to adjust for rainy weather conditions on the day. Her English is perfect, and she speaks a few other languages as well.
Martha met us at the airport with a car and driver, so we could start touring right away. When we could use public transportation, or a walking tour - we didn't pay for the car. Towards the end of the second day, she sent the driver to pick our luggage up from the hotel while we were last minute shopping and again, this saved us time.
I can't say enough about using Martha for such a short stay - we didn't waste time waiting around for public transportation or wondering where to go when Sugarloaf was covered in mist. We ate at local restaurants - we thoroughly enjoyed the introduction to true Brazilian cuisine. She also found us a most wonderful little Bossa Nova Bar which was a great way to spend our last night in Brazil, across the street from the bar where Antonio Carlos Jobim composed 'The Girl from Ipanema".
My 20 yr old daughter wanted some last minute shopping - Martha took us to a great store with a huge selection of contemporary and classic Brazilian music and movies, and also to a store that sold only flip-flops - of every design color and style you can imagine!
With a charming personality, a great sense of humor and a knowledge of history, culture and local shopping, we feel we now have a friend in Rio. You can reach her at firstname.lastname@example.org