Just a note to say that I am collecting some security documents at Scribd - about 20 so far. This includes useful documents that I found on the web, plus several written by myself. My documents include information on the Birthday Paradox, Data Centric Security, Black Swans in IT Security, Entropy Bounds on Traffic Confirmation and a host of other topics that I have blogged about in the last year or so.
In general Scribd is a wonderful source of material for a wide range of topics, including security, risk management, probability, general analysis plus a wealth of information on less technical topics. If anything there are now too many documents, but the pockets of gold are worth the search.