I made a switch to Darn Tough (made in Vermont) socks a couple of years ago and haven't looked back- they make 20-30 varieties- thin to thick, low to high, multi colored, etc

 

they have a lifetime warranty and I've sent in 3 or 4 pairs over the last couple of years and have gotten new ones in return in a weeks time

 

for trail running in the cooler weather I prefer their merino 1/4 cushion, for warmer weather their 1/4 merino mesh; they also make non-merino cool-max socks as well

+1 to Darn Tough

Like the Smartwool, too, but in recent years they wear out quickly. I have some pair of Darn Tough over 5-6 years old and without much sign of wear.