for my diploma thesis, I need to find information about integration of functional and imperative programming concepts. Could somebody of you point me to good websites, papers, etc. about this topic?

You haven't been too specific about what kinds of things you are looking for. One thing that you might find useful is, http://www.mm.informatik.tu-darmstadt.de/~kuehne/fps/. Also there are plenty of functional-object-oriented languages. Checking the paper listings of FOOL conferences should provide many other papers.