I am a huge fan of the First Lite Aerowool boxer briefs. I had 2 pairs of the Dobson Aerowool briefs and I can certainly attest to their awesomeness.
1-They wick moisture like no other. I never felt swampy in them.
2-I found them to actually dry out faster than any poly/spandex underwear I have worn yet.
3-They resist stink better than anything I have tried. I am a STINKY dude when it comes to sweat. Usually one day or workout in my poly/spandex boxer briefs leaves me in desperate need of a shower and the underwear of a good torching. Not these. Wore them in HOT days in September with ridiculous amounts of sweat with no abnormal or bad smell.
The bad part is that I blew out the seats in both pairs I owned. The weak part wasn't the merino. It was where the mesh panel was. The merino just wasn't stretchy enough so it put too much stress on the thin mesh panel. Too bad since they cost $45 a pair and only lasted me 2 years. I just ordered 2 new pairs of the Wick line and have worn one pair for a couple days. The Wicks are much improved. They are just as stretchy as my spandex briefs and the mesh panel appears much more durable and integrated into the wool, which when coupled with the added stretch, should hopefully eliminate any failures. Most comfortable underwear I have ever owned. If you get them, however, be sure to size down. I wear a Large in their pants but the medium long boxer briefs are a perfect fit.
If you don't like the merino, the Ex-Officio give'n'go sport briefs are also nice as others have said. I have one pair and they breathe very nicely and don't stink nearly as much as pure spandex or poly skivvies. My only beef with them is they pill like no other. After one wear and one wash, the face fabric literally went from silky smooth to feeling like a billion little cotton balls. They literally looked like they aged 3 years overnight. It is disappointing as those weren't cheap either, but luckily, it doesn't seem to affect their performance at all. Just seems cheesy to pill up so fast. Seems the older versions didn't have this problem. Its probably because the fabric is so thin. They seem rather durable other than that though. No holes or wearing through yet.