The best website to use for train schedules throughout Hungary is http://www.mav-start.hu/. It has updated train schedules for all trains within Hungary as well as international trains coming from or going to stops in Hungary. The schedules are clear, and the site tells who if and when you have to change lines on a trip. A great way to plan a quick trip from from Budapest or elsewhere. There is also a link to the Die Bahn site for other European timetables. It is great to be armed with information from this website, especially since English is not always spoken at the train stations for domestic trips.
Website: http://www.mav-start.hu/