Website: Art of the Rifle Blog
Several years ago I stumbled on an unpretentious site called Artoftherifleblog.com. The author has set out to master the rifle (or come as close as humanly possible). He's analytical, disciplined, and a good writer. His posts mostly focus on bolt action rifle craft (much carries over to semi-auto rifles), but there's a smattering of other gun or freedom related content. When I first discovered the site I spent a number of hours reading through all the archived posts, which was well worth it.
To get you started, here's some noteworthy posts of his:
Why the Rifle? - An explanation on why riflecraft is important
Rifle Ten: A test of rifle skill devised by Jeff Cooper
And lastly, look over the Reference Section for a lot of his articles grouped by content type. Enjoy!