The 2004 Let's Go book said that Tomar was at the end of a minor line & might require changing trains to get there....that's either false or no longer true. Trains run from the Lisbon Oriente station every few hours and take about 2 hours to get to Tomar.
Beware the ride back to Lisbon from Tomar in the morning as the train fills completely with commuters after the 2nd or 3rd stop.
Tomar is at the end of the line, which means you are likely to have to change trains to get in or out of the town, usually at Entroncamento. You can easily drop into Tomar on your way between Lisbon and Porto, and it won't add much more than an hour or so to your journey. It's takes about an hour or two to Lisbon and costs 7-8 euros. This is a direct route. The trip to Porto requires a change at Entroncamento where you will join the rapid inter city train that will whisk you the rest of the way. The journey costs about 18 euros and takes around 3 hours.
I went to Tomar from Porto by an express bus, it was a double-decker, fast, cheap and comfortable. The bust station is in walking distance from Tourist Office and the centrum of the town.
I went from Tomar to Evora by an express bus via Lisbon - it is about 4 hours, fast, comfortable. The problems are: that in Tomar bus station no one understands English and the buses are always late. Ours was too, arrived in Lisbon 2 minutes before the Evora bus left. So I am happy that I had learnt the word VIATURA which is the line number and onde é (where is) and á esquerda (on the left), á direita (on the right), em fronte (straight on) nad caught my bus.
Why do we guys feel the need to name our cars? I don't know, but my buddy Pav and I called our little Fiat Punto rental car, "Quicksilver." This little car took us all over central Portugal and saved us some money by getting good gas mileage. You'll probably want to park outside of the Old Quarter above the River Nabao. We parked just on the edge of it, on Rua Santa Iria.
This train was sitting unattended in Praça da Republica and I can only assume that it was there to take tourists up to the convent on the hill, but I'm not sure.