Filibusters and Cloture in the Senate
http://www.fas.org/sgp/crs/misc/RL30360.pdf
Reviews the rules of the Senate which make filibusters and other obstructive tactics possible, how cloture can be used to choke off filibusters, and how the threat of filibusters can lead to compromises and other effects, both desirable and undesirable. From the Congressional Research Service, posted by the Federation of American Scientists