If you are not familiar with Megabus, it is an intercity Bus service that is pretty famous for their low fares. Their wikipedia description attached below.
Megabus website: http://uk.megabus.com
" Megabus, branded as megabus.com, is an intercity bus service of Coach USA/Coach Canada and DATTCO (a non Stagecoach company, under contract) providing discount travel services since 2006, operating throughout the eastern,southern, midwestern, and western United States and in the Canadian provinces of Ontario and Quebec. Megabus is notable for using curbside bus stops instead of traditional stations, low fares starting at $1, and in recent years, operating a point-to-point network of routes with buses making few stops en route to their destination. "
I took the Megabus for the following routes; Paris to Cologne. From Rome to Venice. From Venice to Milan and from Milan to Paris.