A new paper called "Deanonymisation of clients in Bitcoin P2P network" by Biryukov, Khovratovich and Pustogarov from the University of Luxembourg has been published on arxiv.org.
In contrast to the usual offerings, it's actually quite good.

The authors explain how to deny the use of TOR to connect to the bitcoin network by sending enough short messages of a particular form to get all the TOR exit nodes banned.
They analyze a method of discovering the 8 peers to which an average node maintains a connection thereby discovering the network topology.
They outline a DOS attack using ADDR flooding
They outline a method of rapidly lowering the difficulty under certain circumstances by constructing an "Alternate Reality". (A bit less exciting than it sounds!)

There are some other substantial chunks of experiment and analysis as well as some pretty graphs.

Probably the best constructed paper I've seen on Bitcoin.

ByteCoin