I am planning a trip to Germany and need some help finding intercity bus routes. I want to start in Nuremburg then on to Regensburg, Harburg, Dinkelsbuhl, and Rothenburg, and possibbly ending in Heidelburg. As near as I can tell, most of these towns do not have rail service so I am hoping that I can find bus service between these towns. Where can I find that information?
As far as I can tell, they all have stations except Dinkelsbühl.
See Rail map of Bavaria here: http://www.bahn.de/regional/view/mdb/pv/deutschland_erleben/bayern/regionales/diverses/mdb_86722_streckennetz_bayern_2012.pdf
Or for Baden-Württemberg here: http://www.bahn.de/regional/view/mdb/pv/deutschland_erleben/baden-wuerttemberg/regionales/baden-wuerttemberg-ticket/2013/mdb_117821_streckenkarte_bawue_2013.pdf
The German railways website will find you connections to these places including buses if needed. Be sure to enter the correct spellings, Nürnberg, Dinkelsbühl, Harburg(Schwab), Rothenburg ob der Tauber and Heidelberg.
Chris is right. All of the places you mention have rail service except Dinkelsbuehl (alt spelling for Dinkelsbühl).
You can get to Dinkelsbühl by bus from Nördlingen (a better town to visit, IMO, than Dinkelsbühl), the next town north of Harburg on the rail line from Augsburg.
You can get from Dinkelsbühl to Rothenburg by bus with a change of buses in Dombühl or by bus to Ansbach and by train to Rothenburg with a change of trains in Steinach.
You can get the rail and bus schedules from the German Rail website. If you can't make Umlauts (those two dots over a vowel) adding an 'e' (ue for ü, etc) is acceptable (and historically correct). All of the rail travel can be done with point-point tickets or with a Bayern-Ticket (23€ for one person). Some of the bus segments might be covered by the Bayern-Ticket. In 2007, when I did the Romantic Road in short segments, spending time in towns along the way - overnights in Oberammergau, Landsberg, Nördlingen, Feuchtwangen, Weikersheim, and Würzburg - I spent less each day on the bus than what a Bayern-Ticket would have cost.
On the Bahn Query page, be sure to specify Harburg (Schwab). There are other Harburgs in Germany. The station in Harburg is a km south of town, and there is no public transportation from the station to town, but it is not a bad walk along the road. The climb from town to the castle is another thing. There are also no lockers at the station. I put my bag in a locker in the station at Donauwörth, 11 minutes away to the south, went to Harburg, then went back to Donauwörth to retrieve my bags and then past Harburg to Nördlingen. You'll have 18 minutes in Donauwörth to retrieve your bag.