Museums run by the Government are free on Sunday until 2pm. Gulbenkien museum is free on Sundays
The City Hall organizes free concerts during the summer time. Keep your eyes open for these. A favorite of ours is the Africa Festival, which in 2006 and 2007 was held in July at the Tower of Belém.
For archaeology and architecture enthusiasts, the Millennium Bank headquarters in Lisbon, on the Rua dos Correeiros no. 9, offer a free archaeological tour of the cavernous area under the bank explaining how Pombaline architecture works at the foundation level, and showing ancient Roman villas. Tours run 3-5pm on Thursdays and Saturdays from 9am-1pm and from 3-5pm. Highly recommended!
Agenda LX is the free monthly magazine available across the city providing a full cultural agenda for the city. Nice design and beautiful photos. Follow Me Lisbon is a simpler, free tourist agenda available widely. Also Convida Lisboa has a neighborhood-themed restaurant and shopping guide of top quality available around town. There’s no need to buy magazines or papers for cultural calendars.