Flixbus.de introduce a new bus route from Berlin via Dresden and Prague to Vienna. It operates as day and as overnight journey.
Also quite useful is their route from Erlangen via Nuremberg, Munich Airport, Munich Hbf, Salzburg, Linz, Wachau to Vienna (and back). Also the company operates busses from Munich via Regensburg and Plzen to Prague.
They operate Zurich via. St. Gallen to Munich and Koblenz to Berlin.
Another popular route, in addition to all of their domestic routes, is Rostock (for Warnemünde cruise port) to Berlin or to Hamburg.
Their route map is here: https://www.flixbus.de/streckenuebersicht