Just adding to Greg's accurate post about the Lisbon Marriott...
While the Aeroshuttle is an option at 3.50 Euros, a taxi from the airport is usually no more than 10 Euros (on weekends, when it's higher and including the 1.60 Euro per bag surcharge, and tip).
That said, Lisbon taxi drivers are famous for gouging people to or from (usually from) the airport, especially Americans.