The Fenian Movement.
http://www.historylearningsite.co.uk/fenian_movement.htm
http://www.irishidentity.com/stories/fenians.htm
The Great Famine, 1845-1850.
http://www.historylearningsite.co.uk/ireland_great_famine_of_1845.htm
http://dartmed.dartmouth.edu/winter10/html/faculty_focus_we/excerpt.pdf
Excellent treatise on the causes of the famine.
http://www.rootsweb.ancestry.com/~irlkik/ihm/ire1841.htm
Provides an annotated map of Ireland, circa 1841, detailing housing and literacy information and an extensive breakdown in population decline, County by County.
http://www.ego4u.com/en/read-on/countries/ireland/great-famine
Offers a discussion of the Irish Famine within the context of broader contemporary European events.
Ireland and Land Problems
http://www.historylearningsite.co.uk/ireland_%20land_%20problems.htm
Ireland’s History
http://www.historyireland.com/
This is a fantastic searchable site that contains a huge amount of information over the full range of Irish history, including between 1841 and 1854.