All counties have now been added to the National Archives of Ireland's free 1911 census website. The 1901 and 1911 censuses are the only surviving full censuses of Ireland open to the public. Both censuses cover the entire island of Ireland. The 1911 census was taken on 2 April 1911.
Ireland's census records are unusual in that the original household manuscript returns survive. These are the forms filled out and signed by the head of each household on census night. Most other countries only have enumerators' books, where family details were transcribed by the person charged with collecting the census information. In Irish records, you can see your ancestor's handwriting, assuming that he or she was the head of household at the time.
By end-September, the National Archives of Ireland expects to be re-developing the site to include full transcription of all of the data on the household forms for 1911, including religion, occupation, relationship to head of family, literacy status, marital status, county or country of origin, Irish language proficiency, specified illnesses, and child survival information.
1901 Census material, with all data transcribed, will be launched between late 2009 and early 2010.
You will find the National Archives of Ireland's 1911 census website at: http://www.census.nationalarchives.ie.