Some history of Spacewar! (And some wistful stuff about E. E. “Doc” Smith). Link
Hey, a bunch of Doc’s books are on Gutenberg! Here’s the one that got me hooked, when I was about 10. (My dad’s comment when he pulled it off my bookshelf years later and read it: “Hey, I grew up in Idaho on a farm, and got a PhD too!”)
Turns out that some of John W Campbell’s books are on Gutenberg, too (link), though the most readable of his works (The Mightiest Machine) are not. (I just found out that there’s a sequel to TMM, but it’s long out of print, very expensive, and reportedly nowhere near as good).