RRuDi is a research corpus for linguistic inquiries into the history of the Russian language. It forms the main source of evidence for the research project "Korpuslinguistik und diachrone Syntax: Zur Grammatikalisierung peripherer Subjekte in slavischen Sprachen" (2008-2011), funded by the German Research Foundation.
ACT, the software we use for annotation, for the corpus database and the respective web interface, is, unfortunately, no longer publicly available. We are grateful to Kiril Ribarov and his collaborators for still being able to use their system. Find out more about ACT in Ribarov et al. (2004): ACT - Computer Processing of Written Cultural Heritage Sources.
Melanie Gau has written a recent U Regensburg master's thesis on diachronic corpora, giving and overview about the current state of the art. You can view it here. Please quote it as
Gau, Melanie (2005): The State of Historical Corpus Linguistics with Special Focus on the Russian Language. M.A. thesis, University of Regensburg, Institute for Slavonic Languages and Literatures.
Roland Meyer's (2005) article on general encoding issues and the first (pre-ReACT) version of the corpus