I may be leaving this prematurely because we are leaving our luggage tomorrow, but it appears that this is a service that Lisbon is sorely lacking! Each train station only has 12 lockers each (good luck!) and aren't as centrally located. It is right down the street from Praca de Luis Camoes You can hang out in the waiting room, print boarding passes make photocopies, etc. nice clean place and the guy was very friendly. Looks like about 1 euro per bag per hour, a little more or less, depending on size and length of time.
Seems completely worth it if you want to enjoy an afternoon in Lisboa without dragging a suitcase around what must be the worst cobblestones and the #*$@$@$& narrowest sidewalks I have ever seen. Or just walk in the streets and get plastado'd by a nutso tram driver. You won't have to worry about your flight at all. read more