I'm very excited this morning, the National Archives of Ireland has put the Tithe Applotments online! http://www.genealogy.nationalarchives.ie/ Along with Soldier's Wills and the censuses of 1901 and 1911. Well, not so excited about the censuses, they were already available, but the Tithes are a really big deal. Given the paucity of Irish records from the early part of the 19th century, they are a great asset. A description of the tithes can be found here: http://www.irishtimes.com/ancestor/browse/records/land/tiap.htm
I was disappointed to find the Civil Parish of Graney in Kildare, home to the McGarrs, has somehow been omitted, but I've dashed off a note to the Archives and I'm hoping that will be remedied. Good luck searching.