Additional general resources, statistics and overviews:
Country guides from various diplomatic services:
Library of Congress:
Colombia: A Country Study - Note: this was published in 1990, so should only be referenced for non-dated information.
Wikipedia entry:
Colombia - Note: wikis may be edited by anyone, so while the information here may be more up-to-date, there are also reliability issues, as persons may alter information. Any information on a controversial topic, such as narcotics trafficking or the role of the autodefensas, should be verified by other sources.
EDITED TO ADD: Country Profile from the Library of Congress:
http://lcweb2.loc.gov/frd/cs/profiles/Colombia.pdf . Basically, a 26-page country study updating and summarizing the main country study. PDF format. Dated December 2004.