This is the best site for train travel out there in my opinion. It has everything you will ever need to now about travelling on rails anywhere in the world. They have the most in depth information on times, train conditions, routes and prices. This site is a must for for any train trip you might encounter.
Google Maps is also an amazing site for getting around. By adding point A and Point B it’ll show you multiple options on how to get there, plus how long and what type of transport. With the offline maps function as well you will never be without a map.
Rome2Rio is another great website for comparing you transport needs. It gives you options on how to get from where you are, to where your going. Once you have entered your departure and destination details it will give you all the train, bus, plane, car, ferry routes that can take you there and the costs. I would always start with this company as it gives you a rough guide at what is possible.
Visiting this region of Europe is tricky to travel around on a tight time frame. There is little information concerning public transport from country to country. The best site we could find was Balkan Viator. Not to be confused with Viator this site concentrates on buses going from place to place. Accurate on times and duration, it is a must for anybody thinking about visiting.