Figures in 28mm-Musketeers are gorgeous.
I think Liberation makes a more complete line in 20mm
Rules-Leo Cronin's "Black and Tan Wars" if you can get them. Not really skirmish rules, and not for big battles, but unlike anything else I have ever played.
I use TFL's through the Mud and Blood for skirmish. The Triumphand Standards supplement for those rules has some background and 3 scenarios, the last of which is reflects one of the larger actions of the conflict.
Not a fan of "Michael Collins", but I did like "The Wind that Shakes the Barley" (sorry Carlos)
Books-on my shelf I have:
Michael Hopkinson-The Irish War of Independence.
Guerilla Days-Tom Barry
British Voices of the Irish War of Independence (HIGHLY recommended)
Curious Journey-Oral History of Ireland's Unfinished Revolution (not bad if you can get through the intro)
Raids and Rallies-Ernie O'Malley-the first several chapters are full of scenario ideas
Gallowglass presents a very good list of resources here:
http://leadadventureforum.com/index.php?topic=5924.30