I recently read Tim Pat Coogan's Michael Collins and it had a passing mention or two of GAA from a sporting standpoint. Obviously you have the Hogan stand, but I've hear vague accusations over the years of the GAA and IRA being mutually supportive beings. I get the casual cultural connections - and that any athletes among the men would have probably been players themselves - but were there any higher-level links? How about during the Troubles? I know there are clubs like Kevin Lynch's Hurling Club.
Not a formal link, but Tommy Ryan was in the same Tipp side as Michael Hogan on Bloody Sunday and was a loyal IRA man. Served as an officer on the pro-Treaty side of the Civil War and was buried with full honours when he passed away.
Not so much with The Troubles time GAA but then again it wasn't for people to broadcast that they were in The IRA but I’m looking for a more definitive source. As a lot off the GAA’s higher ups are still alive so it would be pretty difficult to find any certainties about membership. However, one of the founders of the GAA was a supporter of the IRB. His names Michael Cusack and he was a supporter of and Irish Ireland. Also there is a.. person from Northern Ireland called Willie Frazer who has some theories about the GAA and the IRA that you may find amusing.