Traveling by bus may be preferable to traveling by train. This is especially true in Croatia, Serbia, Bosnia, Albania, Turkey, Latvia, Lithuania and Estonia. These countries are not well-connected by rail. Not only might you pay more to take the train, you may not be able to get everywhere you want.
Traveling by bus may not be as comfortable as traveling by train since you can't move around as much. However, it may be your best options.
Two bus companies have created passes similar to the Eurail: