Don't know how long these have been available, and searchable for free. They can be found at: http://www.census.nationalarchives.ie/search/
I'm accustomed to searching census records in the US, and was saddened to learn that earlier Irish ones had, with a few exceptions, been destroyed. However, I was amazed to see the level of detail for the rural and small town families I was looking up. Be sure to look at the additional forms to see who owned the land, what sort of house it was, what kind of outbuildings (fowl house, piggery, etc.)and what the living conditions were of the immediate neighbors. I also used Google satellite view for more info on what an area looked like in the present, and for street names.
I did have to be creative in finding the town of Aughnacloy in County Tyrone. It was indexed as Aughancloy, though the forms themselves were correct.