http://www.cotralspa.it/ENG/Index.aspBTW, take the Rome metro to Ponte Mammolo, exit Metro, go upstairs to buy ticket for bus to Tivoli (don't exit at street level where the other bus stops are, you have to go upstairs to the Tivoli bus). The ticket seller will confirm for you where to stand and wait (there are several platforms upstairs, but there's also a digital screen telling you which is Tivoli bus). Must add, since this bus goes outside Rome area, you can't use the 75 minute ticket you used on the Metro even if it's still valid. You need to buy a separate ticket for the Tivoli bus.
We missed the mass at San Giorgio Maggiore; the entrance to that church is at the very back of the church you intially walk into. By the time we found the entrance to the other church, it was locked. But we could still hear the singing through the door.
We didn't go to the Basillica Di Santa Maria or the Accademia in Venice - we chose to shop instead.