Deeds are sometimes some of the better research sources as tracking land you know your ancestors occupied leads to information that might be used. However, very few records are online, but the good news is someone is doing Deeds, Probate, Abstracts and so on — with most things an Index is indespensible and something that is needed. Perhaps someone will build one in the future?
Some available resources Ireland (please forward any new or other sites in comments):
http://freepages.genealogy.rootsweb.ancestry.com/~registryofdeeds/by_number/indexed.htm
http://search.ancestry.com/search/db.aspx?dbid=28911
http://search.ancestry.com/search/db.aspx?dbid=28911