With BitIodine you can find connecting paths between two Bitcoin addresses, visualize clusters controlled by the same user or entity, and get insights about activity on the network.
More info at: http://miki.it/articles/papers/#bitiodine.
On Ubuntu:
apt-get install libssl-dev cmake build-essential g++-4.4 libdb++-dev libboost-all-dev libsparsehash-dev git-core perl sqlite3 python3-numpy python3-simplejson python3-networkx libhiredis-dev libsqlite3-dev