euroRail pass is the cheapest way to travel once you are there.. The cheapest way is to go directly to an airline's website and search the sight for lowest fares and dates.. . None of the travel sights sell tickets for all of the airlines...missing, most notably, are the low-fare carriers e.g. Southwest, airTran, Jet Blue, etc.. . Very often I've looked up fares on the travel sights and found what I thought to be a good deal. But then I'd go to a low-fare carrier's website and find a walk-up fare that is much lower than a so-called legacy carrier airline's discount fare that is offered by a travel sight.. . For ease though, any of the travel sights works fine. You'll pay more for the ticket, but won't have to spend a lot of time over several days checking each airline's websites.. . A list of all airlines websites and a eurorail link can be found at airlineflightinformation.com