The Armstrong Clan Society has a great selection of genealogy, published articles, & as links to other Family History sites.
Chronicles of the Armstrongs is a great book available to read free online! Published in 1902, it's one of the most comprehensive works on the family I've ever read. Our greatest challenge has been bridging the gap between 1780's and the mid 1600's. Once completed, we'll have a greater picture of the life the lived and the challenges they faced every day.
If you love old photos like I do, be sure to look at the Irish Historical Picture Company. It's organized by county as well as town and city with an amazing selection to choose from.
If you have a favorite website or book on the Armstrong families, I'd love to hear from you!