Delaney (Delany, Deleany, Delane, etc)

#1 About 1150 A.D. the northern section of Ossory (Co. Laois) held the sept of Ua Dubhslaine (O'Delany or O'Dulany) of Coill Uachtarach who were noted as chiefs of Tuath-an-Toraidh. Delany is a surname never seen today with the prefix O which probably belongs to it. It is O Dubhshlainte in Irish, Delaney being a phonetic rendering of this - the A of Delaney was formerly pronounced broad. An earlier anglicized form was O'Dulany e.g. Felix O'Dulany, Bishop of Ossory from 1178 to 1202, who built St. Canice's Cathedral in Kilkenny. Dubh means black and slainte is topographical - Slaney in English. If it refers to the river Slaney it suggests that this sept originally possessed a wider territory than that usually assigned to it, namely Coilluachtarach (now Upperwoods) at the foot of Slieve Bloom near the source of the rivers Nore and Barrow in Co. Leix.

#2 In its form, Delaney is a Norman name, from De l'aunaie, meaning "from the alder grove", and doubtless some of those bearing the name in Ireland are of Norman stock. However, in the vast majority of cases, it was adopted as the anglicised form of the original Irish Ó Dubhshláine, from dubh, meaning "black" and slan, meaning "defiance". The original territory of the Ó Dubhshlaine was at the foot of the Slieve Bloom mountains in Co. Laois. From there they spread also in neighbouring Co. Kilkenny, and the surname is still strongly associated with these two counties.

Online sites for Ireland/Delaney:
Search birth, marriage death at Irish Family History Foundation website.
A good guide to Irish research in general is FIANNA. There are some surname specific areas, but a true wealth of information overall.
The Delaney page at the IrishTimes site. As with all Irish sites, you'll pay through the nose to do more than search.
Griffith's Valuation: Published between 1847 and 1864, this was the first full-scale valuation of propterty (landlords and lessees) in Ireland. This is the best site for the Griffith's Valuation I've found so far. You can see transcriptions and the original book pages for FREE.

Delaney Forum Message Boards:
Delaney @ Rootsweb
Delaney @ GenForum
Delaney @ CuriousFox