This summer I am looking at traveling to cities in Poland and Czech Republic with no airline service. Over the past five years I have used Flixbus and Ecolines for travel across Central Europe and the Baltics where bus service is the fastest and often the cheapest way to travel between many cities in these regions. Many of these buses offer free wifi and seat-back monitors with movies, music and games. Some long distance bus services have an attendant for drink and food purchases.
Finding bus routes from one city to another
Flixbus has a useful feature that allows you to select a city and see all the other cities you can reach from there directly by Flixbus. This proved very useful for me in figuring out how to travel across the western portion of Poland efficiently without too much backtracking. And provided much shorter travel time and distance than train service for places I want to visit.
Flixbus Route Map
Flixbus is a Munich based company that has been swallowing up other regional bus companies like Polskibus in Poland (another bus company I used for several trips) and even operates some USA western states routes. Flixbus has extensive route coverage across most of Europe.
Ecolines Bus Route map
Ecolines is based in Riga, Latvia and covers many Eastern Europe locations in the Baltics, Belarus, Ukraine and points in Russia not covered by Flixbus.
A couple other sites I regularly check for planning travel around Europe include: