Hi
If you have any Irish ancestors and who hasn't? - this site is a must. It has lots of links to sites freely giving information. Warning - keep away from Ancestry as it's not free. I had a look at Piggots 1824 Provincial Directory and Slaters 1846 Commercial Directory of Ireland and found interesting stuff in them.
This is a great site and well worth exploring.
Happy hunting.
Jim
http://www.censusfinder.com/ireland.htm