Did it in the summer from Venice through Italy down to Ancona and then through Croatia, Hungary, CZ and up to Berlin. Worked out that it was cheaper to book all the trains individually than to get an inter-rail pass - yeah, you're stuck for which train you can go on but you have to pay to reserve a seat even with a pass. Also, there were parts that were more convenient/only doable by bus (Croatian coast) and that was dirt cheap.
The sites mentioned above are great for train times. Double-check once you're there as we found an overnight train that only went 3 nights a week so scuppered our plans a bit.