My husband is descended from the Clannaboy (Antrim) O'Neill family (Shane's son, Art O'Neill) and the Crebilly (Sligo) O'Hara family (Art O'Neill married Grace, daughter of Cahall/Cathal/Cathall/Charles O'Hara. Grace was the sister of Sheela who married Philem O'Neill, Art's brother.) These happened prior to 1600.
This site is excellent for O'Neill and Ulster in general:
Royal O'Neill
http://www.cgocable.net/~aoneill/homepg.htm
(The O'Neills and O'Haras above are mentioned in Royal Gen Part 2, under 126b.)

I am seeking more about the O'Hara line, aware it has a long documented lineage. I understand they are listed in John Burke's Gen and Heraldic Hist. However, they are not listed in the original version from the 1830s (which is reprinted and the only version I can find either at DAR or the Library of Congress.) The Crebilly O'Hara family is described in the Vol3 Supplement of 1860 and Vol4 from 1863.
Thanks,
Bonnie Butler
skyvine@aol.com
(My website will be up soon.)