Ask Metafilter to the rescue ...
Read the following thread for a touching account of how a man living in Washington DC posted on AskMetafilter to find out the address of where his grandfather lived in Vienna before he fled (during WWII). Someone from the Holocaust Museum (another reader of Ask Mefi) responded within 32 minutes of posting. He and a colleague of his, were able to trace down a large amount of information about the grandfather. A very touching story, - only that it is real.Read the full thread
here
.