A nice bouquet of useful links is offered by the HABSBURG Net, only partially repeating what you could find at the sites enlisted above.
Eastern German Studies Association
Students of the former GDR (Deutsche Demokratische Republik) will find the site of the Eastern German Studies Association extremely useful.
School of Slavonic and East European Studies
The WEB-site of the School of Slavonic and East European Studies, University of London, constitutes a most useful starting point for scholarly web-surfers involved in the study of eastern Europe and the lands of the former Soviet Union.
The REESWeb is sponsored by the Center for Russian and East European Studies of the University of Pittsburgh, a National Resource Center in the USA for Russian and East European Studies.
Slavic Research Center
The collection of links offered at the WEB-site of the Slavic Research Center of Hokkaido University provides an excellent platform from where you may reach a great deal of what is relevant for students of Eastern Europe on the web.