Aerobus operates three routes to main spots of the city.
Aerobus 1 running every 20 min follows Av. da Republica and Av. da Liberdade to the city center (Rossio, Praça do Comércio, and railway/ferry terminal at Cais do Sodré).
Aerobus 2 connects to the Oriente bus/railway terminals with 30 min interval.
Aerobus 3 runs every 30 min to the central bus station at Sete Rios via the Entrecampos train station. Tickets cost €3.50.
Note that Aerobus tickets no longer include unlimited public transportation, they are only valid for the Aerobus.
Aerobus website: http://www.carris.pt/fotos/editor2/citycenter.pdf