sock and underwear fabrics

Wool liner socks are fine.

I'd avoid the cotton blend underwear.

You are going to get a lot of different responses on socks. Some will tell you dont worry about the liner, others that you got to have it. My personal preference is a medium weight wool ankle sock with no liner.

Bottom line with socks is that all of our feet are different. My opinion is that socks are something you have to personalize with what works for you. That may mean trying different combinations to find what works best for you. The one thing I think we can all agree on – no cotton!

I use nylon for both.

Liner socks will get hammered a bit. Nylon ones are fine, but I think thin wool ones will wear out very quickly.
Cotton is cheap for socks but pretty horrible for walking.

Underwear – cotton blend is OK, just a bit slow drying. Straight syn is OK if done properly, and dries faster.

I use Gobi Wigwam liner socks and ExOfficio briefs.

Cheers

+1 on what Caffin said.

Personally I wear wrightsocks that come with with a built in liner and while not as durable as I would like (a pair or two seemed to thin quickly), I still have yet to wear a hole in any pair of mine (the oldest pairs are 3 years old or so).

For underwear you'll find a ton of happy users of Ex-Officio boxer/briefs on this site, myself included. (I'm even wearing a pair now if that's not enough testimonial ;)

I know I'm gonna catch some flack, but I bought some new micro fiber underwear at Macys last week. They were around $10-11/pair (Calvin Klein). And just tried a few times so far, but they are super comfortable. Hope to try a pair on a hike this weekend. Very breathable and nice to the touch. 50 grams for superman style and 72 grams for boxer style.

Also, I really like compression shorts. I have several pair I got at Big5. They are Everlast and can be had for around $10 on sale. Very reliable and could be used as a swim suit in a pinch. They are long enough to prevent chaffing and dry very fast when you wash them. I think they are nylon. Very trail tested and highly recommendable.

Cotton kills in sock and underwear fabrics especially.