I am especially interested in good examples where historians have been able to pose and preferably answer new (or old) historical questions through the use of topic modelling?
I can provide two examples of US-american historians: Sharon Block used topic modelling to investigate the content of the Pennsylvania Gazette from 1728-1800 (see the article here: http://www.common-place.org/vol-06/no-02/tales/). And Cameron Blevins investigated a historical diary containing over 10.000 entries between 1785 and 1812 (http://historying.org/2010/04/01/topic-modeling-martha-ballards-diary/).
I suggest the "New Electronic Museum of the City" (Nu.M.E.) of Bologna. It was a University of Bologna study (began in 1999/2000) on the medieval aspect of the city. They started from historical sources (documents and iconographic sources) using computer graphic as a mean to visualise and validate theories and hypothesis. You can start looking at the english version of the project's website: http://www.storiaeinformatica.it/nume/english/ntitolo_eng.html